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BUILD YOUR OWN HANOI-TALKIE! 



Build this 
liigh-efficiency 

HANOI-TALKIE 

for business or amateui 
communications ^ 

Build our — 

REFLEX TESTER 

and find out just ^ 
how fast you are! ^ 

How to use the IB 

555 TIMER CHIP 1 

to build 

oscillator circuits 
Build a 

250-WATT 
POWER INVERTER 

to supply 120 volts AC 
from 12 volts DC! 

Use our ^ 

PC-BASED 

TEST BENCH ^ 

to identify and test ^ 
digital IC's 



CombtnBd 
with 



est 

$3.75 CAN i ' 



Bectroaics 




FLUKE AKD THILtrS - THE GLOBAI ALLIANCE IH TEST & MEASUREMENT 



FLUKI 



PHIUPS 



PHILIPS I 



Introducing SCOPEMETEK. 




There's More Than One Reason to Reach for It. 

Ill (acl there's evety reason to reach lor ScopeMeter/ Becaose only ScopeMeler 
combines the expertise of Fluke and Philips to bring you a dual-channel digital scope 
along with everything youVe come to expect from Fluke digital multimeters. 

The result: an integrated scope-and-multimeter that lets you see a waveform and 
digital meter display at the same time from the same input. Or switch betv/een 
dedicated high-performance Scope and Meter functions with the touch of a 
key. That makes it faster and easier than ever to capture, store and analyze 
precisely what you're looking for. At a prme Ifral looks good. too. 
To get your hands on a ScopeMeler, contact your Fluke sales office or your nearest 
Ruke dtstnbutor For more product information, cafi 1-800-44-FlUKE 

SCOPEMETER* Now there's only one to reach for. Simply Easy. 

• Intuitive front panel layout for 
simple, slfaiflhtforv/ard operation, 

• Pop-up menus and five function 
keys for easy conUol- 

• Autos et automatically sets voltage, 
time and tngger functions. 

« Saleiy^Sjgned BHC connectors 
and probes simplify ftaating 



Built toTake It. 

• Completely sealed against water, 
dusl and contaminants, 
• Ef^l protected and measures 
up to 600 volts rms 
• Rugged construction with 
shock' reststanl holster 
» Thfee-v-ear warranty 





Goes Wherever You Go. 

• Runs on rechargea&le PJiCad Batteries 
slandard C-celEs otthe included line 
voltage adapter "battery charger 

• Ad|ustaii?t tih-stanlTianger 

• COfnpatibfe if/ith a wide range of 
Buke mu^i meter accessories. 



CIRCLE 121 ON FREE INFORMATION CARD 



W 




i 



October 1992 ^^^^ 

m. 63 No 10 



35 HANOI TALKIE 

Use this efficient mini FM transceiver for business or amateur 

communtcattons. 

Doti Wray 

43 REFLEX TIMER 

Find out just how fast your reflexes are! 
Dan Kennedy 

61 DIFFERENTIAL PROBE 

Make safe measurements in ungrounded systems. 
Walter Dorfman 



47 PC-BASED TEST BENCH 

Build the TtOOa digital logic fC tester. 
Steve Wolfe 

75 250-WATT POWER INVERTER 

Use it to power small appliances from your car 
James Melton 

TECHNOLOGY 

55 NOT WORKING TO NETWORKING 

Case histories of some problem LAN's. 
Gary McClellan 

69 THE 555: A VERSATILE OSCILLATOR 

Learn to use the 555 IC in circuits that waiL warble, and honk! 
Ray M. Marston 



7d HARDWARE HACKER 

Histograph equalization. 
Don Lancaster 

88 DRAWING BOARD 

Video scrambling. 
Robert Gross blatt 

97 COMPUTER 
CONNECTIONS 

Miniature multimedia. 
Jeff Holtxman 



8 VIDEO NEWS 

What's new in this fast- 
changing field. 
David Lachenbrucli 



16 



EQUIPMENT REPORT 

Computer monitor checker 



78 AUDIO UPDATE 

Syndicated reviewers, AM 
stereo, and consumer fraud. 
Larry Klein 



84JtLp THIS 

REFLEX TIMER 





PAGE 43 



250 WATT 
POWER 



INVERTER 










J 


■ 



PAGE 75 



105 Advertising and Sales 
Offices 

1 06 Advertising index 
97 Buyer's Market 

4 Editorial 

14 Letters 

32 New Lit 

22 New Products 

12 Q&A 

6 What's News 



Whether you need a handheld 
transceiver for business or for ama- 
teur-radio — or just want to build one 
for the fun of it — ou r Handi-Talkie has 
a lot to recommend it. The small, 
tight-weight transceiver is powerful 
and efficient, offers narrow-band 
FM modulation and can be designed 
to operate anywhere from 27 to 32 
MHz — and even up to 60 MHz with 
minor parts changes! That config- 
uration allows the Handi-Talkie to 
work both the six- and ten-meter 
amateur-radio bands. Thanks to the 
use of surface mount technology, the 
whole devicei including a re- 
chargeable nickel-cadmium battery 
pack, is housed in a case less than 
six inches long. Turn to page 35 for 
all the details? 

COMING NEXT MONTH 

THE NOVEMBER ISSUE 
GOES ON SALE 
OCTOBER 6. 

PHOTO SOUND STROBE 

This project brings the worlds of electron tcs and photography 
together to capture exciting, astounding images on film. 




SOLAR EVENT MONITOR 
Keep track of magnetic-field anomalies that can disrupt 
hance — communications. 



en- 



CIRCUIT COOKBOOK 

A variety of astable- and monostable multivibrator circuits based 
on the 555 timer. 

AUTOMOTIVE POWER RELAY 

This "smart" switch is perfect for controlling such high-current 
devices as auxiliary lights and high-power audio amplifiers. 

As » tQAiic« 10 Fead#rf. ELECTHONICS NOW pybli^Hes avithbfv plana or inifofni»tiDn rvUting to npwjA&fthy ptoducli. 
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nfttfult ind worlunanship utvi by readsrs. ELECTRONICS NC^ di$daim« «ny rfMponsib^lity for tha %Af« and pnpmr 
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Bectroms 

NOW. 

Hugo C«msba€k 1 1 604- 1 9673 foumtef 

Larry St«ckl«r, EHE CET. 
odftor-in- chief and publisher 

EOlTORtAL DEPAmiMENT 
Brian C. Fenton, i^ditor 
M«rc Spiwattp associate editor 
N^H Sclater» associate editor 
Tart Sf^dutOt assistant editor 
Jflffrsy Holtzman 

computer editor 
Rob«rt GrossblJittt circuits editor 
Lurry Klein, audio editor 
David Lachenbnjch 

conthbutin'g editor 
Don Lancaster 

contributing editor 
Katliy Tflranzii editorial assistant 

JUTT DEPARTMENT 
Andre Duzant» art director 
Injcie Leo* illustrator 
Rus»«tl C* Truelsoni illustrator 

PftOOUCTION DEPARTM£ffT 
Ruby M. Vh* prDductton director 
Karen 5. 8rown 

advertising |>roduction 
Marcel la Amoroso 

produ ctio n n^tstant 
Lisa Rachowftx 

editorial product! ori 

CIRCULATiON OEPARTIMENT 
Jacquellno P* Chaoseboro 

circulation director 

Wandy Alanko 

circulation analyst 
Thar*sa Lombardo 

circulation assistant 
MIcHela TorHtlo 

reprint bookstore 

Typography by hAates Graphics 
Cover photo by Oivoretfied PhvtO 
Services 

Electronics How fs indexed In 

Applied Schnc9 d Techoofogy index, 
and Hoadmrs Guida to P^riodic^ Utvr- 
Ature^ Acmdemie Abstracti, and 
MugjLfrVte ArUcfe SwnmAti^. 
Microftlm & Microfiche editions ere 
available. Contact circulation depart* 
mem for details, 

Advertisfng Sales Offices Us led 
an page 102. 

Elftctronica Now Executive and 
Administrative OfTtcos 

Subs^Rier Customer Service: 

1-800-288^52. 
Order Entry for Mew Subscribers: 

1,800-909^7139. 



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NOW'S THE TIME 



Now, according to Webster*s New World Dictionary, means "at the 
present time; at this moment." Electronics Now is just what its 
name implies: a compilation of what is happening in electronics at 
this moment! 

Electronics Now brings you the latest news, the newest products, 
the most useful training, the most exciting projects, the newest 
how-to information. We help you learn how it works, how to keep it 
working, and, of course, how to make your own. We even show 
you what may happen tomorrow. 

Above all else, we remain your electronics magazine. We know 
that the great majority (89%) of you earn your living in electronics. 
But you are the engineers and technicians to whom being an 
electronics professional is more than just a job. In your spare 
time — your leisure time — your personal time— you still want to 
know and learn more about electronics. 

You want to know how Caller ID works. You want to know how 
digital audio tape compares to digital compact cassettes. You need 
to know about cellular telephone services and the personal 
communication networks of tomorrow. You need to know what 
microprocessor your next computer will have. You have to know 
what the next generation ICs will be like. 

Bringing you information on those and other subjects is our forte. 
We work and strive to stay on top, to learn, to explore, and follow 
late-breaking developments in electronics. And we do it now! 
That's where our new name — Electronics Now— comes from. 
That's what we bring to you — today and tomorrow — 
Electronics Now! 

Stay with us as we evolve and grow to meet the ever growing 
challenge of the electronics revolution. Stay with us as we continue 
our quest for the most exciting, most revolutionary, and most 
daring developments of today and tomorrow. Become, through our 
pages, a part of the most important and influential segment of our 
modern world- Come with us as we become Electronics Now. 




Larry Steckler. EHF/CET 
Editor-in-Chief and Publisher 



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WHAT'S NEWS 



A review of the latest happenings in electronics. 



64-tnegabyte memory chip 

A computer memory chip jointly 
developed by engineers at IBM (Es- 
sex Junction. VD and Siemens can 
store more than 64-million bits of 
data — four times the capacity of the 
most advanced memory chip in 
computers today. 

The new dynamic random access 
memory (DRAM) chip can store the 
equivalent of about 6000 pages of 
double-spaced typewritten text, 
and can "read'' mom than 64'mHlion 
bits on the chrp in a fraction of a 
second. The chip measures 
lOJmm by tS.Imm (appnoximately 
%-mch by ^-inchX 

The chip was developed with an 
advanced CMOS technology pro- 
cess. Its smallest conductive traces 
are 0.4 micrometers wide, about 
one two-hundredth of the thickness 
of a human hain The transistor' gate 
insulator, a nonconducting layer that 
separates conducting layers on the 
chip,measures only 10 nanometers 
in thickness. 

The electrical charges that make 
up each bit of information are stored 
in a buried-plate trench eel A con- 



ductive FBgion in this cell is diffused 
from the bottom part of the trench 
into the substrate. That region 
serves as the common buried-plate 
contact to all the cells. The tnsncb s 
sidewalls are covered with an in- 
sulating material and the trench is 
then filled with conductive silicon. 
Informatton is stored in the material 
inside the trench. 

The entire trench area occupies 
only 1,5 square micrometers. The 
cell is so small that needy one mil- 
lion of them can fit on the head of a 
pin. 

The 64-megabit chip, which oper- 
ates from 3 single 3.3-volt power 
supply, has borderless contacts 
that eliminate the necessity for 
providing a border around the metal 
that forms electrical contacts to 
specific areas of the chip.Bor* 
deHess contacts reduce the area of 
the chip 

IBM and Siemens began their 
joint development on the chip in 
January 1990. Their goal is to have 
the chip ready for mass production 
by the middle of the decade. 

In July IBM announced that it is 




A SERIES OF MEMORY CELLS IN THE IBM/SIEMENS64-fn[lllon-bjt compyter memory 
chip 3S seen with an electron microscope. 



joining with Siemens and Toshiba to 
develop 256-megabit DRAMS. 

Faster silicon circuits 

We sting house Electric 
CorpCPittsburgh, PA) has received 
a government contract to develop 
silicon transistors that operate at 
higher speeds than todays devices. 
The new technology is expected to 
extend the use of low-cost silicon 
substrates into the higher-frBCfuen- 
cy regions of radan cellular tele- 
phones, digital radio, and ultra high- 
speed computing. 

The $624,000 U.S. Navy Re- 
search Laboratory contract, which 
extends through the end of 1993. 
supports further development of 
the silicon-on-insulator tech- 
nology — called Microx. The tech- 
nology will be used for applications 
in which both microwave radio and 
digital functions ane built into the 
same monolithic chip. 

Experimental microelectronic 
chips fabricated from Microx have 
operated at the mfcruwave frequen- 
cies of 30 GHZ and they are ex- 
pected to achieve 40 GHz, 
smoothing the way to a new genera- 
tion of low-cost, mixed function RF/ 
digital silicon monolithic circuits 
whose speeds ate comparable to 
those attained by gallium-arsenide 
devices. Westinghouse believes 
these to be the highest frequencies 
ever reported for linear MOS silicon 
transistors. 

The key inpiovations am ion-im- 
planted oxide layers produced with- 
in a high-iBSistfVity substrate that 
resembles an insulator, combined 
with several advanced fabrication 
techniques. According to Michael 
C. Driver, manager of micro- 
electnDnics at the Westinghouse 
Science & Technology Center. Mi- 
crox can realize at least 10 decibels 
of power gain at 1 0 GHz. This perfor- 
mance, he said, coupled with the 
low cost typical of silicon MOS 
technology, opens up a broad range 
of applications. R-E 





114.119 





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VIDEO NEWS 



Whafs new in the fast-changing video industry. 



DAVID LACHENDRUCH 



• Digital TV gains* There has 
been a notable shift in the direction 
of the world HDTV winds m the last 
few months. Despite the fact that 
both Europe and Japan are theo- 
rettcafly committed to analog sys- 
tems, the United States suddenly 
has assumed unquestioned lead- 
ership in the HDTV field. Progress 
here in digital HDTV— and proof 
thai digital systems actually can 
work — has sent shock waves 
through Japanese and European 
television circles. Now, for the first 
lime, engineers in both regions are 
looking seriously at digital systems, 
and predicting thai their countries 
"ultimately" will go digital, 

Japan. In Japan, where the ana- 
log MUSE Hi' Vision s^tem is actu- 
ally being broadcast by satellite for 
eight hours daily, engineers arB be- 
ginning to forecast an eventual 
switch over to a digital compressed 
system. Japan's commercial broad- 
casters have always been slightly ill 
at ease over the publicly supported, 
non-commercial NHK network's es- 
pousal of Hi- Vision, but for direct 
satellite broadcast only. The Hi-Vi* 
sion system is now almost 20 years 
old and it ignores some of the newer 
technologies employed in other 
HDTV systems. Prices of HDTV re* 
ceivers have been coming down- 
but from the rarefied level of 
$30,000 to the still high $10,000— 
and sales have been extremely 
slow. 

One manufacturers view Digital 
HDTV is "quite likely to be the wave 
of the future" in Japan, said Hiroyuki 
Mizuno in the keynote address to 
the International Conference on 
Consumer Electronics (ICCE) in 
June, the annual meeting of Amer- 
ica s consumer-electronics engi- 
neers in Chicago. The statement is 
significant because Mizuno is ex- 
ecutive vice president of Mat- 
sushita Electric, the worid's largest 
producer of consumer electronics. 
Mizuno called the analog Hi-Vtsion 



system a "bird in the hand." giving 
the Japanese people and TV set 
manufacturers experience in high 
definition. 

But Mizuno said digital HDTV will 
^Inevitably fuse" the TV and the 
computer, making TV a '"digital mul- 
timedia bn^adcast station which can 
pnDcess, store, create, and transmit 
video images " Conceding that "we 
are experiencing temporary tech- 
nical difficulties ' in supplying prac- 
lically priced HDTV receivers and 
VCR s in Japan, he said that these 
problems eventually will be solved, 
but he didn't say whether the solu- 
tion would be digital or analog. 

Europe. Europe £ Eureka project, 
designed to develop an HDTV sys- 
tem different from Japan s. envi- 
sions a two-stage move to HDTV. 
The first stage would be broadcast- 
ing in a widescreen improved sys- 
tem called D2'MAC. followed by a 
move to HD-MAC. a high-definition 
system. However, neither system is 
compatible with the existing PAL 
and SECAM broadcasts in Europe, 
and both systems were designed 
for direct satellite transmission. Eu- 
rope s satellite broadcasters are 
having financial difficulties, and gen- 
erally have refused to adopt MAC 
broadcastrng.preferring to continue 
to use PAL. which ts compatible 
with TV sets there. Despite tremen- 
dous pressure by TV manufacturers 
and proposals to issue large gov- 
ernment subsidies for a 
changeover. MAC'S adoption has 
been sluggish. Europe's broadcast 
authorities, with a nervous eye on 
the HDTV research in the United 
States, have been quietly working 
on digital systems for Europe, With 
the MAC structure coming under 
increasing criticism (for instance, it 
ignores terrestrial broadcasting, 
which produces 90% of the broad- 
cast ad revenues in Europe and has 
more than 90% of the audience), 
demands for a change to digital ter- 
restrial HDTV have been sounded 



more fn&quently in recent months, 
and research toward a digital sys- 
tem has come out of the closet and 
is being discussed openly. 

Just a few years ago, it was popu- 
lar to say that the United States was 
far behind Japan and Europe in 
HDTV. Today, it is accepted that dig- 
ital broadcasting is the wave of the 
future, and that the United States is 
in the vanguard. Officially. Japan 
might be very proud that it was first 
and that its system has been under 
development for 20 years — but that 
makes it a 20-year-old system, in 
contrast to America's up-to-the- 
minute approach to HDTV. 

HDTV set a\/aifabifity. When vi/ill 
HDTV receivers be widely available 
in the United States? The Advanced 
Television Advisory Committee 
CATAC) to the FCC recently set out 
to get the answer, so it sent ques- 
tionnaires to all major TV manufac- 
turers serving the United States 
nnarket — a total of 14. It received 12 
replies, ATAC specifically asked for 
"time of general availability to con- 
sumers from multiple sources" — 
not for the time of shipment of "one 
set per showroom/* 

The replies indicated that HDTV 
sets would be plentiful 2V2 to three 
years after the FCC approves a 
transmission system. That event is 
tentatively scheduled for late 1993. 
However, some respondents replied 
that sets could be available sooner 
if manufacturers take a chance and 
start developing them as soon as 
the advisory committee makes its 
recommendation to the FCC. That 
ts expected in Febnjary 1993. And 
the survey showed that HDTV sys- 
tem proponents that also manufac- 
ture TV sets — Philips, Thomson, 
and Zenith— might have a six- to 
nine-month advantage over their 
competitors. Other manufacturers 
that develop their own ICs might 
have a three-month advantage over 
those that buy chips from others, 
the survey revealed. R-E 



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Write toQ&A, Electronics Now, 500-8 BhCounty Blvd., Farmingdale, NY 11735 



LOCAL BUS 

Tve been hearing a lot about 
local-bus computers, but I can*t 
seem to find a clear definition of 
exactly what they are and why 
they're supposed to be so ter- 
rific. Several computers in the 
mail-order advertisements tout 
the feature, and each one that 
does is quite a bit more expen^ 
sive than similar ones without a 
local bus. Can you explain to me 
in simple terms what a local bus 
is, and whether it's worth the ex- 
tra money?— R Geeben, Ana- 
wana, NY 

All the peripheral cards that plug 
into your computer, such as the vid> 
eo card and others, get their basic 
clock speed from a single pin on the 
bus. The clock speed comes from 



the master oscillator on the mother- 
board, which is usually the one 
that's clocking the microprocesson 

For reasons buried deep in the 
corporate vaults at !BM. the bus 
clock was usually limited to a max- 
imum of 6 or 8 MHz — that was the 
speed of the last of the original AT s 
that had a standard bus. With the 
introduction of the PS/2 series of 
computers. IBM abandoned the old 
standard bus and began using the 
MicroChannel Bus— a different 
thing altogether 

That change left the compatible 
and clone manufacturers in a bit of a 
quandary since they no longer had a 
developing standard From IBM. The 
original AT had a t6-bjt bus because 
that was the internal bus size of the 
80286 (the last microprocessor 



IBM used in the ATX IC's such as the 
386 and 486 are 32-bit micro^ 
processors, but IBM's new 32 bit 
MicroChannel Bus was a proprietary 
bus. The result was a lack of an 
accepted standard for a 32'bit bus. 

With the exception of IBM, com- 
puter manufacturers have recently 
agreed on the EISA (Extended In- 
dustry Standard Architecture) 32- 
bit bus that has shown up in a lot of 
newer PC-compatibles, The gene- 
sis of the local bus is similar. 

While some cards that plug into 
the slots at the back of the mother- 
board have to run at speeds slower 
than the microprocessor, a few 
others are perfectly happy to run at 
microprocessor speeds. A good ex- 
ample of this is the video adapter, 
which can easily be designed to run 



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at speeds higher than those avail- 
able with the standard bus cfocks. 

Along with the adoption of the 
EISA bus. the local bus (S a system 
m which a separate bus is provided 
for certain peripheral cards that 
don*t have to be limiEed to standard 
bus-clock speeds. The result is 
much faster operation, and for 
something such as video, the dif- 
ference is astounding. 

Deciding tf something is worth 
spending money on is a persona! 
decision, so I won't answer that part 
of your question. However, because 
this is a recent development, man- 
ufacturers are just starting to pn3- 
duce iocal-bus peripherals so you 
might want to wait and see what 
develops over the next few months 
and whether a standard takes hold. 

AUDIO CROSSTALK 
I've been getting a lot of 
crosstalk between audio chan- 
nels and, after eliminating every 
other possibility, Tve come to 
the conclusion that the signals 
are leaking through the power 
supply. There doesn^t seem to 



be anything on the circuit 
boards to take care of the prob- 
lem so I guess I'll have to do it 
myself. Could you tell me what 
the basic circuit setup is for 
power-suppiy decoupling?— A. 
MacDonnell, Mill Hill, NY 

If you re sune that the power sup- 
ply is the source of your problem, 
and it turns out that you're right, you 
can consider yourself lucky be- 
cause it's easy to take care of. 

The basic design for power-sup- 
ply decoupling is shown in Fig. 2 
and. as you can see. there isn't 
much to it. You can get a lot more 
involved when you're dealing with 
very high frequencies* but because 
you're only concenried with audio 
Stuff, the layout in Fig, 2 wilf be fine. 

The resistor values should be cal- 
culated by looking at the maximum 
current draw of the equipment and 
applying Ohm's taw. Remember that 
the resistors will be carrying all the 
current needed by the circuit, so 
you should pay pnDper attention to 
their wattage as well. In general, as 
long as you're dealing only with line- 
level stuff, you can use quarter-watt 



FIG. 1— POWER-SUPPLY DECOUPLING 
CIRCUITRY, These circuits can gel a lot 
more complicated, but for audio fre- 
quencies, this Is more than enough. 



resistors and everything will be OK, 
Once you calculate the needed 
resistance (supply voltage/max- 
imum cument)* add another fifty per- 
cent to the value just to be on the 
safe side. Audio levels can vary all 
over the place, and if you*re listen- 
ing to something with a neally wide 
dynamic range, too low a value on 
the resistor wiH cause the signal to 
dtp. 

There's nothing magical about the 
choice of the capacitor value either, 
and Tve used everything from 10 to 
100 |jlF without any noticeable dif- 
ference. You would think that the 
circuit vTOuld call for a non-polarized 
continued on page 15 



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LETTERS 



Write to Letters, Electronics Nom 500-B Bi-County Blvd, Farmingdafe, NY 11735 



Si 



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I 
UJ 

14 



EQUIPMENT REPORT UPDATE 

Thank you for the wonderful 
Equipment Report on our Compu- 
Scope LITE IBM PC-based os- 
cilloscope (Electronics Now. 
August 1992). We wholeheartedly 
agree with you that "PC-based in- 
struments are the leading edge of 
growth for test and measurement " 
Gage has been a major contributor 
to the buildup of that industry for the 
past five years. 

In the same article, three valid 
criticisms were made by your re- 
viewer Because those points have 
also been raised by some of our 
customers around the world, we 
have been working to solve the 
problems. In July 1992 we released 
a new software package called 
GageScope for our complete line of 
CompuScope cards. 

First, we have drastically im- 
proved the hardware installatiorr 
procedure. We have rewritten the 
entire documentation and software 
supplied with the CompuScope 
LfTE card with special emphasis on 
installation. The 112-page manual 
has a 15-page section on board in- 
statiation, full of examples and 
charts on how to configure a new 
I/O address even if the user does 
not know hexadecimal mathe* 
ma tics. 

Second, to improve the descrip- 
tion of the menus in the manual, we 
included a detailed description of 
each menu entry, as well as a 13- 
page tutorial that guides the user 
through the most often-used menu 
commands. 

Finally, to satisfy the needs of 
more sophisticated customers, we 
offer other pn^ducts: CompuScope 
220. a 40-MHz card with up to 8 
megabytes of memory, and Com- 
puScope 250. which samples at 
100 MHz. Our products are being 
used by major organizations such 
as NASA. IBM. Honeywell, and 
Motorola, and hundreds of smaller 
less well known companies and indi- 
vidual customers. 



We think that, overall, your review 
was very positive about the impor- 
tance of PC-based instruments in 
general, and CompuScope LITE in 
particular. We are very excited 
about our coverage in Electronics 
Now. 

MUNEEB KHALID 

Vice Pmsident 

Gage Applied Sciences Inc. 

Montreal Quebec, Canada 




SURFMAN DIODE REVERSAL 

An error appeared in our Surf- 
Man sound gernerator article 
CEIectrorttcs Now. August 
199TX Diode D2 was incorrectly 
drawn reversed in the parts 
placement diagram, Fjg, 2 on 
page 35. However, it is drawn 
correctly in the schematic. Fig. 
1 on page 34. 



IC SUBSTITUTION 

Mr Caristi is to be congratulated 
for his article "Digital Altimeter" 
CRadio- Electronics. May 1992X 

There is one point that concems 
me, however IC3 gives a full-scale 
reading for a 100- millivolt input 
change Cfrom 2.5 to 2.4 volts at pin 
30), which is an effective sensitivity 
of 20 feet per milftvoll. My concern 
is the choice of the LM324 as ICl. 
While it is a very useful chip indeed, 
it does not exhibit low off-set drift 
with temperature. Prospective con- 
structors who think that shortcom- 
ing could be a problem might want 
to consider replacing the LM324 



with four devices such as OP-07 s» 
which have impressively low drift. 
P.M. BRIDGEN 
Reading. Berks,, U.K. 

CLASSfC VrDEO AMPS 
RE-REVISITED 

I enjoyed seeing my article, 
"Classic Video Amps Revisited/* 
published in the June issue of Ra* 
dio-Electronics. Thanksl 

However, in the editing process 
some errors crept in. The first one 
occurs in the second paragraph on 
page 60. The wording implies that 
the 733 is the better choice for use 
in filters; thats not so. The 592 pro- 
vides the greatest attenuation of 
the unwanted signal. I tried to say 
that the the 592 will provide zero 
voltage gain with a high impedance 
across the gain control pins CGIA 
and GIB), the desired design objec- 
tive at those points for those sig- 
nals. In fact, the 733 would be a bad 
choice for this application because 
it provide a minimum 20-dB the- 
oretical gain for the unwanted input 
signals. 

Paragraph four implies that D1 
through D4 are forward biased. Di- 
odes D1 and D2 are reversed biased 
and D3 and D4 are not biased at all 
or only forward biased when an 
overvoltage signal is applied to the 
circuit. That is necessary for input 
protection. 

Also on page 60. Fig. 7 shows SI 
with a shorting bar across the two 
wipers. That connection is incor- 
rect. There should only be an insu- 
lated mechanical connection. 

On page 61 . Q1 in Fig. 9 should 
be a f^NP device and it should be 
labeled 2N4959/2N3906 rather 
than 2N4959/2N3904. Also in Fig. 
9. 03 should be a PNP device. Fig- 
ure 8 can be used to illustrate the 
proper configuration. 

Overall, the article fulfills its ob- 
jective of stating that both the 592 
and 733 video amplifiers are still 
recommended for new designs. 
EDGARDO PEREZ R-E 



O&A 



conlimied from page 13 



capacitor, but my experience is that 
polarized capacitors work just as 
well. Remember that you're not 
dealing with high current and volt- 
age levels here, and that gives you a 
considerable amount of leeway. 

LINE-LEVEL DIFFERENCE 
I've noticed that there s a con- 
siderable difference in the audio 
level that conies out of my CD, 
tuner, cassette player, and other 
equipment. When I switch my 
amplifier from one source to an- 
other I can often hear a dramatic 
difference in the levels. Is there 
some way to buffer those sig- 
nals between the equipment and 
the inputs to my power amp so 
the levels presented to the amp 
are all the same?— D. Gould, 
Michigan City, IN 

You can call them buffers, but as 
fares I can see, what you really need 
is a preamp on each line so you can 
adjust the level from each device 
before it gets to the power-amp in- 
puts. A lot of the consumer audio 
equipment on the market really 
cheaps out when it comes to the 
output level. The cassette and CD 
players on my sheli for example, 
are top of the line units, but neither 
of them has a convenient fft>nt panel 
control for adjusting the output 
level. 

There are really three ways you 
can handle this pmblem. The first, 
and easiest, ts simply to drop all the 
levels to that of the lowest one with 
simple resistor pads. Once you've 
done that, you can set the power- 
amp level and not have to change it 
every time you switch from one 
source to another. 

The second way to deal with this 
involves a bit more work, but is not 
really all that difficult. Although 
there s no front-panel control for the 
output level, you can bet your new 
pair of white tennis shoes that 
there's a trimmer somewhere inside 
each of the players that sets the 
output level. Just get yourself a 
screwdriver take the cover off, and 
start exploring. It's a good idea to 
have the service manual around 



when you do this, but most of the 
consumer audio stuff l*ve seen has 
the function of the trimmer 
silkscreened on the printed-arcuit 
board. 

The last approach to the problem 
is to build a bunch of preamps with 
line-level inputs and outputs. You 
can put them between the equip- 
ment and the power amp and adjust 
the levels that way. Td do that only 
as a last resort. It's a lot more work 



because you1l need two preamps 
for each piece of equipment (as- 
summg. of course, that you*re deal- 
ing with stereo). Besides the extra 
work. IVe never been convinced 
that it s a good thing to have more 
electronics on the line than the bare 
minimum required. That's because 
any extra electronics is a potential 
noise generator and also a potential 
entryway for externally produced 
noise. R-E 




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15 



EQUIPMENT REPORTS 



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use. and more in the wings. One 
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The Checker, a new product from 
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was designed with that in mind. Al- 
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cian, or for anyone who manages or 
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The Checker is packaged in a rec- 
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put modes: CGA Ccobr graphics 
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Using the Checker ts slraighifor- 
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Even though the Checker is 
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suspect monitor with one that is 
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step is basic, simple troubleshoot- 
ing to narrow down the problem. 



Unfortunately, that simple meth- 
od has its own problems. First is the 
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ited space that is available at the 
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enough room to work conveniently 
The handheld Checker weighs less 
than a pound, and permits a monitor 
check to be done in just a minute or 
two. 

For afyone who maintains an in- 
ventory of computer monitors* the 
Checker could also come in handy. 
Is the monitor that is to be installed 
for that new employee workir^g? The 
Checker lets you find out beforByou 
haul a non-working monitor over to 
the installation site. 

The Checker also has a place in 
professional service shops. It can 
be used, for example, to "bum in" a 
monitor without tying up special 
test equipment or a computer (with, 
of course, the correct graphics card 
installed.) When a customer comes 
in to pick up his monitor, the Check- 
er makes an ideal way to demon- 
strate that the repair was suc- 
cessful and that the monitor is now 



working pn^perly. It can also be used 
as an aid in setting vertical and hori- 
zontal size controls correctly. 

The Checker does not support 
Hercules-type monochrome 
monitors. That's an unfortunate 
oversight in our opinion. Although 
such monitors are not popular sell- 
ers these days, there are an awful 
lot of older units in circulation, and 
older equipment is more likely to 
develop problems. We would also 
have preferred to see an SVGA 
(super VGA) mode and test pat- 
terns more useful than the non- 
standard color bars that are pro- 
vided. 

With a price of $229.95, the 
Checker is far too expensive for ca- 
sual use. Hov^^ver. the speed and 
ease writh which the Checker can 
provide a go/no-go indication would 
be welcome by anyone who spends 
a lot of time checking a lot of 
monitors. When you consider the 
amount of time that the device could 
potentially save, and the headaches 
it could help prevent, the Checker 
could prove to be a worthwhile pur- 
chase. R-E 




The World is Talking! 



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re's viHir "uide 
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also from Ultra-X, to identify' 
individual defective RAM chips, 
locate interfacing problems, and 
pinpoint defective support chips. 

This ingenious diagnostic 
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LOGIC PROBE. Beckman In- 
dusthai's LP50 is an inex- 
pensive, small 50-MHz 
logic probe that can detect 
pulses as short as tO 
nanoseconds. The pen-siz- 
ed logic probe is intended 
for iroubleshoobng high- 
speed, microprocessor- 
conlrolled circuits and the 
detection of extrenriely fast 
pulses. According to Beck- 
man, the probe measures 
TTL DTL. and RTL logic 
levels at frequencies up to 
50 MHz. 

The LP50 is powered 
from the circuit under test 
through an alligator clip 
that prwides a secure con- 
nection to circuit ground. 
The mmi'hook clips onto 
the circuit's positive volt- 
age points. When the 
probe tip is touched to the 




OIICILE 16 ON FREE 
INFORMATION CARD 



signal test point, the probe 
simultaneously lights an d 
LED and generates a tone 
to make it easy for the user 
to understand what is hap- 
pening at the test point. 



The LP50 logic probe is 
priced at $45 — Beckman 
Industrial Corporatiorr, 3883 
Rutfin Road, San DiGgo, CA 
92123-1898; Phone; 
619'495-3218. 



GABLE TV SIGNAL'LEVEL 
METER. Leader Instru- 
ments Model 951 RF sig- 
naMevel meter is intended 
for broadcast and cable TV 
measurements. It features 
autO'Channel search to 
measure the store level 
data for up to 32 channels. 
The LED bargraph dispfay 
is arranged in groups of 
eight channels and it pro- 
vides readout of the se- 
lected channel in dBmV or 
other user-selectable engi- 
neering units. 

Autoranging is featured 
but manual ranging can be 
selected. The Model 951 
also operates in the single- 
channel mode with a com- 
bination bargraph and dig- 
ital readout of leve! in 
selected engineering units. 
The meters operation can 



be programmed for video 
or sound-carrier levels of 
channels selected by the 
operator. 



< 



CIRCLE 17 ON FREE 
INFORMATION CARD 

Frequency data for the 
USA and other countnes 
are stored. Up to 32 chan- 
nel fBadings can be stored. 
DC and AC voltages on the 
cable can a!so be read. The 
portable instrument mea- 
s u re s 8 % X 4 % X 7 Vs- 
inches and it weighs 10!/2 
pounds. Powered by D 



cells, it has an auto-off fea- 
ture that extends operating 
time. 

The Model 951 CATV/ 
TV signal level meter has a 
p rice of $ 1 695.— Leader In- 
strument Corporation. 380 
Oser Avenue, Hauppauge. 
NY 11 788: Phone: 
1-800-645-5104 or 
516-231-6900 in New York. 

KEYBOARD-CONTROLLED 
POWER SUPPLIES. Kepcos 
DPS Series of keyboard- 
controlled power supplies 
provide 75 watts of DC 
power in four ranges from 0 
to125 volts. Eachpower 
supply is controlled by a 
keypad that commands a 
built-in microprocessor to 
set voltage, current limit* 
range, over voltage protec- 
tion COVP). displays, and 



over-current protection- 
Remote talk-listen con- 
teol can be exercised with 
an RS'232C connection 
that can be addressed in 
Basic and most common 
computer languages. Key- 
pad slew controls permit 
continuous adjustment of 
voltage up and down for 
fine tuning while the output 
is enabled. Separate LED 
displays provide voltage 
and current readout. 




CIRCLE 1H ON FREE 
iNFORiMATION CARD 

DSP power supplies are 
priced at $429.— Kepco, 
Inc.. 131-38 Sanford Ave- 
nue. Rushing. NY 11352: 
Phone: 718*461-7000; Fax: 
718-767^1102. 

MULTIFUNCTION OUTLET 
TESTER, Polytronics Sure- 
Test Pro Multifunction Out- 
let Tester is said to be able 
to pnDvide a higher level of 
assurance of power delsv* 
ery than conventional volt* 
age meters in situations 
where the power source is 
critical. 

The meter test for cur- 
rent capability by creating a 
12-ampene load on the line. 
Applied in short intervals, 
the 12-annpere power draw 
can reveal the presence of 
a faulty circuit breaker or a 
sag in power delivery 
(greater than 5%) due to 
poor contacts or improper 
wiring. 



A MUST FOR OEMs AND MROs! 

THE NEW NTE PARTS CROSS REFERENCE AND 
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cincue Tt ON fhei information card 




CIRCLE 1<J0NFREE 
INFORMATION 0\ID 



The SureTest Pro tests 
seven outlet parameters: 
miswines and inconnect wir- 
ing, praper voltage and cur- 
rent capability, ground 
faults (6-milliannpere trip 
current), ground/neutral 
voltage latch, ground/neu- 
tral short, and high ground 
impedance. The unit is 
plugged into an outlet, and 
LED indicators pfDvlde go/ 
no-go readouts for all 
tests. 

The SureTest Pro multi* 
function outlet tester CRart 
No. 413B200) is priced at 
$179.— Jensen Tools Inc.. 
7815 South 46th Street. 
Phoenix, AZ 85044: 
Phone: 602-968-6231 

HEAVY-DUTY CABLE TEST 

CLIP. iTT Pomona's Mode! 
5784 test clip permits the 
probing of insulated wires 
or cables without stripping 
the insulation. It is intended 
for use in laboratories, auto 
service shops and factory 
maintenance facilities. The 
clip is said to assure 
positive efectrical contact 
and true readings, and it 
provides safe high-voltage 
lead testing with operator 
protection of up to 1000 
volts AC. 
The spring- loaded test 




CIRCLE 2QONFREI 
INFORMATION CARD 



probe has a heavy-duty, 
statnless-steel needle 
point set within a clamp- 
type jaw, allowing the clip lo 
pierce the insulation of a 
cable up to 0.t4-inch 
C3.5mm) rn diameter with- 
out damaging the insula- 
tion. The insulated tip 
assures that the desired 
wire or cable is safely and 
firmly grasped, and it 
avoids contact and shorts 
or grounding to adjacent 
machinery. A socket for a 
sheathed test lead connec- 
tion Is located in the plung- 
er handle. 

Model 5784 clips are 
priced at $12.30 each— ITT 
Pomona Electronics. 1500 
East Ninth Street. RO. Box 
2767. Pomona. CA 91769: 
Phone: 714-469-2900: 
Fax: 714-629-3317. 

SWT PROTOTYPING 
BOARD. The SMT-WOO 
protoboard from Precision 
Circuit Technologies allows 
for the placement of more 
than one !C on the board. 
Measuring 2,9x4.75 
inches, it permits the pro- 
totyping of circuits with 
many IC s. 




CIRCLE 21 ON FRH 
INFORMATION CARD 



Each SMT pad is con- 
nected to a plated-through 
hote that interconnects it to 
other points on the board 
with wire links. Two power 
busses simplify power con* 
nections. Most of the 
board's part footprints will 
accommodate more than 
one part size. The 
S0IC-16S will accommo- 
date 8', 14-. or 16-pin 
SOICs: the SOIC-20W will 



accommodate a 16*or 20- 
pin wide-body SOIC or an 
8%14-.orl6-pmSOIC: and 
the SOIC-24W will accom- 
modate a 16-. 20% or 24- 
pin wide-body SOIC or an 
8% 14-, or 16-pin SOIC. 

Two PLCC areas permit 
great selection of PLCC 
sizes (20- to 100-pin 
PLCC's). A small section 
with through-hole pads 
spaced at 0,1 -inch is avail- 
able for combinsed AMD 
and leaded assembly. 

SMT-WOO protoboards 
are priced at $18.95 
each.— Precision Circuit 
Technologies. 10378 Fair 
view Ave.. Suite 152. 
Boise, ID 83704; Phone: 
208-327^0300. Ext, 2200, 

SELF-PULSATING USER DI- 
ODE. The RLD Series of 
self-pulsating, single-long- 
itudinal mode. AIGaAs 
laser diodes from Rohm 
Electronics can, according 
to the manufacturer, re- 
duce the cost of fiber-optic 
transmission in LAN s and 
WAN's. The double-het- 
erostructure laser diodes 
can be modulated at fre* 
quencies of L2 GHz. 

The high modulation he* 
quencies are achieved 
through the low junction ca* 
pacitance of the dies ac* 
tive area. They are man- 
ufactured by the molecular 
beam epitaxy (MBE) pro- 
cess which permits atomic- 
layer control in the growth 
of the striiclune. This, ac- 
cording to ROHM givers 
better control than is ob- 
taine with either liquid- 
phase epitaxy CLPE) or 
metaiorganic chemical 
vapor deposition 
CMOCVD). 

RLD Series laser diodes 
typically operate at a 
th reshold current of only 32 
milliamperes, significantly 
lowering power consump- 
tion, increasing switching 
speed, and giving longer 
operating life. Recent ac- 
celerated life tests of the 




ORCLE 22 ON FREE 
INFORMATION CARD 



laser diodes by ROHM on 
one sample lot at 50*" C 
with a constant 3 milliwatt 
optical output showed a 
mean time to failure of 
240,000 hours. This figure 
compares with the 20.000 
hours typical for laser di- 
odes in compact and video 
disk players. 

RID laser diodes are 
priced below $30 each in 
volume,— Rohm Corpora- 
tion, addness. Antioch, TN. 

COMMUNICATIONS RE- 
CEIVER. According to its 
manufacturer the Lowe 
HF'150 communications 
receiver puts the entire ra- 
dio spectrum from 30 kHz 
to 30 MHz at your finger* 
tips. That gives the listener 
access to international 
shortwave bands, amateur, 
ship and aircraft bands, 
and time signals . The tuning 
rate is variable according lo 
the rotation speed of the 
main tuning knob. 

This rugged portable re- 
ceiver is made with solid 
hard alloy casings, metal 
panels and machined 
parts. It measures only 
7.3x3.2x6.3 inches and 
weighs only 2.9 pounds. It 
can be operated from an 
AC to DC adaptor (sup- 
plied), an external 10 to 
15 — volt DC source, or 
eight internal nicke!- cad- 
mium rechargeable AA 
ceils for 150 milliampere 
drain. 

Reception modes are 
AM. upper sideband 
CUSB). and lower sideband 
CLSB). which also allows 
reception of CW/RTTY/ 
Fax. A phase-locked AM 



A Shocking OHerl 



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Now you don't have to be enrolled at CIE to receive our 
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BOOKSTORE 

1776 East 17th Street 
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Total Merchandise: 

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Cmt It it ON FREE 
INFORMATION CARD 

system allows mception of 
selection of either syn* 
chronous lower sideband 
or synchronous upper side- 
band, and synchronous 
double Sideband. That ar- 
rangement obtains the 
best reception from weak 
shortwave signals. 

In the dual-conversion 
design, the IF bandwidths 
of 2.5 kHz and 7 kHz are 
selectable, and the master 
oscillators are quartz crys- 
tals. Tuning frequency is 
displayed on a 5-digil LCD 
that also shows modes » 



memory information, and 
other important operating 
functions. Sixty memory 
channels, each storing fre- 
quency and mode, are pro- 
vided. 

The loudspeaker is inter- 
nal. Provision is made for 
external connections to 
headphones, external loud- 
speaker and output for a 
tape recording. The re- 
ceiver can accept three dif- 
ferent antennas: 600-ohm 
long v^re, 50-ohm coaxial 
feed, or a high-rmpedance 
whip. The rear panel has a 
socket for an optional key- 
pad. which allows direct 
frequency entry and instant 
direct memory access. 

The HF'JSO receiver is 
priced under S600.— Elec- 
tronie Equipment Bank. 323 
Mill Street N.E., Vienna. 
VA 22180; Phone: 
703 368*3270; Fax: 
703-938-691 1, 



AUTORANGING DIGITAL 
MULTIMETERS. The 

Tektronix DM25 W and 
DM25tOG digital multi- 
meters, designed for 
benchtop use. offer full 
programmabrlity with 416- 
digit accuracy an integral 
power supply and auto- 
ranging or manual opera- 
tion. Functions provided by 
both units include voltage, 
cument. or resistance mea- 
surement, true RfvIS AC 
voltage measurement 
(200-millivolts to 500-volt 
range), dB calculation, and 




CIRCLE 24 ON FREE 
INFORMATION CARD 



temperature measure* 
ments. 

The meters measure DC 
voWs from 200 millivolts to 
1000 volts with 0.03% 
basic DC voltage accuracy 
and DC amperes Fram 100 
microamperes to 10 am* 
peres with 0.06% basic DC 
amperes accuracy. Both 
units are programmable, 
and the DM25 WG offers 
full programmability with its 
IEEE^4a8.1 interface. 

Front'panel keys simplify 
the selection of function 
and range, and pemnit the 
setting of GPIB address 
and termrnation param- 
eters. The TM2500 Series 
DMM s can be stacked to- 
gether with other products 
in the TektnDnix Tfv1250 or 
TM2500 Series to save 
bench space. Besides de- 
sign, manufacturing, and 
service applications, The 
DMMs are said to have 




The RiV5225 was 
built around sim- 
plicity. Instead 
of a barrage of 
buttons to push, 
you simply 
scroll through a 
menu of special 
functions. 
Minimums, 




■23.29i 




maximums and 
automatic read- 
ing hold are 
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AUTOMATIC flCL METER, 

Fluke's PM 6303A auto- 
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trical dimension and one of 
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ENCYCLOPEDIA OF ELEC- 
TRONIC CIRCUITS: Volume 
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William Sheets. TAB Books, 
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BUILD YOUR OWN SPEC- 
TRUM ANALYZER; by Murray 
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34 



BUILD THIS 



HANDI-TALKIE 



DON WRAY 



IP YOU EVER WANTED TO liUIUU A 

small powerful handheld Irans- 
cciver and, at the same Ume 
leam surface-mount technology 
(SMT), this is the project for 
you! The E'Comni frequency- 
modulated (FMJ transceiver is 
housed in a rugged yet attrac- 
tive aluminum case less than 
six inches long. It is one of the 
most unusual transmitter-re- 
ceivers ever designed for Us 
power level and operating fre- 
quency range. The case In- 
cludes a rechargeable nickel- 
cadmium power pack that will 
save you the cost of periodically 
replacing eight AA alkaline 
cells. 

The E-Comm receiver has a 
respectable 0,3-mlerovolt sen- 
sitivity (l2-dB SINADl for high 
quality reception, and its trans- 
mitter" boasts at least a 90% effi- 
ciency. E-Comm owes its effi- 
ciency to its innovative Ctass-E 
final am pi in er which exhibits 
high power gain. It offers a con- 
tinuous output of 3 watts rms 
into a 50-ohm antenna or 
dummy load. The efficient re- 
ceiver and the rechargeable 
power supply make it possible 
to keep E-Comm on the air in 
the squelch mode tor 80 liours 
without recharging the power 
pack. 

Intended for narrow-band 
FM. E'Comm has a usable car- 
rier frequency range of 27 MHz 
to 32 MHz with only crystal and 
alignmenl changes. The subject 
of this article is a version de- 
signed for 27, 145 -MHz opera- 
tion. With modilications to the 
transmit and receive filters 
(component value changes) op- 
eration up to 60 MHz is possi- 
ble. This allows the transceiver 
to work both the six- and ten- 
meter amateur radio bands. 
Note: This transceiver has not 



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100K 



FIG. 1— SCHEMATIC SHOWJNG THE MODULATOaTRIPLER, Ciass-E amplifier limiter, 
driver and lo w*voUage regu lator sections of the E-Gomm transceiver TTie key device fs 
ECl, the FM transmitter chip. 



5il 



o 
'c 

e 
1 

UJ 



36 



been submitted for FCC ap- 
provai, and its operation on cer- 
tain frequencies may not be 
allowed and/or may require li- 
censing. 

The top panel controls of E- 
Comm include an on-off 
switch. VOLUME and soltklcm 
knobs and an LED power-pack 
status indicator. The removable 
flexible seven-inch antenna is 
coupled to the transceiver with 
a 50-ohm bayonet^style BNC 
connector plug. All the compo- 
nents except the battery pack, 
microphone, and speaker are 
mounted on the double-sided 
PC board. Extensive use of Inte- 
grated circuits and surface- 
mounted components allows 
the circuitrv' to fit on a PC board 
that measures only 2.25 x 3. 1 
inches. 

How it was designed 

The transceiver has three 
main sections: transmltten re- 



ceiver and power supply (Refer 
to Figs. 1 and 2, J The transmit- 
ter is designed around Motor- 
ola's MC2833, a low-power FM 
transmitter IC whose plnout 
and functional block diagram 
are given in Fig. 3. The receiver 
Is designed around Motorola's 
MC3363, a low-power, dual-con- 
version FM receiver IC whose pi- 
nout and block diagram are 
given In Fig. 4. 

Received signals picked up by 
the antenna are preselected by 
the five-pole transmit bandpass 
filter consisting of inductors L4, 
L7. and L5 and capacitors Cll, 
C2, and C30 as shown on the 
right side of Fig, 1, The received 
signal is then fed through the 
receive/transmit switch Sl-b to 
an impedance-matching stage 
consisting of CIO and L3 shown 
on the left side of Fig. 2, That 
stage provides an additional 
two poles of preselection. 

Diodes Dl and D2 prevent 



overloading and the possible de- 
struction of the RF amplifier 
transistor if It is subjected to 
overdriving at the front end. 
The preselected signal is then 
amplified by the 1C3 (MC3363) 
internal common-emitter RF 
amplifier stage and fed to the 
first mixer stage on pin 1. 

The RF amplifier provides a 
gain of approximately 20 dB, 
The first local oscillator (LO) 
takes a third overtone from a 
crystal, and drives the first mix- 
er through an internal cascode 
amplifier. Downconversion 
makes the first LO frequency 
(the first IF frequency) 10,7 MHz 
greater than the carrier. For ex- 
ample, if a 27.145 MHz carrier 
were present, the crystal fre- 
quency would be 27.145 MHz 
plus 10.7 MHz or 37.845 MHx. 

The mixer is a doubly bal- 
anced multiplier that provides 
about 18 dB of conversion gain. 
The output of the mixer is an 
emitter-follower stage with an 
output impedance of 330 ohms 
to match the ceramic fiiten Fil- 





1ST 




iNPirt 


IKPUT 


mt 


VCAP ZOH 




1ST 
LOTANK 

1ST 




iQVm 




1ST LO OUT 


2NDL0 


1STMIK 


BASE 


OUTPUT 


2«IDIin 

QUTPUT 


oumn 




ZNDMX 
IHPUT 










LIMITER 

D£COUPU 


MUTE OUT 


LiMmn 

CHCOUPLE 


COMP 
OUTFUT 


MOlflOft 


COMF 
INPUT 






DfTICi 


REC AUOIO 


QUAD COIL 


MUTI 
(NPUT 




DtttwiuR 



FIG.2^SCHEMATIC SHOWING FM RECEIVER, audio filter, and audio amplifier sec- 
tions of the E-Comm transceiver. The key device here is IC3» Ihe duai-con version FM 
receiver chip. 



ler F2, a 10.7-MHz ceramic 
bandpass filler, removes un- 
wanted out-of-band harmonics 
from the ouipul of the first mix- 
en The second mLxer takes a sig- 
nal from the 10.245-MHz funda- 
mental mode crystal-controlled 
oscillator XTAL2 whose output 
Is mixed with the 10.7-MHz first 
IF to generate the 455'kHz sec- 
ond IF with a conversion gain of 
approximately 21 dB, 

The 455-KHz ceramic filler Fl 
(left side of 1C3 in Fig. 2) prt>- 
vides narrow-band filtering for 
Ihe limiter ampilfiers within 



TCI. the MC2833 FM transmit- 
ter chip. The limtters clip the 
455-kHz second IF signal to re- 
move unwanted amplltude- 
modulaled signals and feed the 
audio detector A quadrature de- 
tector within ICS, the MC3363. 
detects the modulated signaL 
The parallel quadrature detec- 
tor tank, LIO. in the detector is 
tuned to 455 KHz. 

The demodulated (audio) sig- 
nal on pin 16 of the FM trans- 
mitter ICl is then filtered by an 
active filler stage that includes 
an op-amp within IC3* the FM 



receiv^er chip in Fig. 2. This ac- 
tive filter, connected at pins 15 
and 19 of 1C3 and consisting of 
capacitors C13, C24. and C15 
and resistors R21, R22, R23, 
and R15, has a rolloff at 3 kHz 
Squelch Is performed by the 
carrier-detect function on pin 
13 of the FM transmitter chip. 
iCl in Fig. L Resistor RIO (be- 
tween pins 12 and 13) provides 
hysteresis in the squelch circuit 
to prevent unwanted "break 
through/' This squelch circuit 
is unusual; Its output both en- 
ables and disables iC4. a 
Motorola MC341I9D low-power 
audio amplifier with a chip dis* 
ABLE pin 1 (CD)* 



o 

O 
cr 



JO 

m 

S 
n 

Z 

o 



37 



VARIWLE 
REACTANCE 



RF 
OSC 



^ ♦ Wf I BUFFER 



Aamp 

S4 




IS 



PARTS LIST 



15 



14 



10 



m 



FIG. 3---PIN0UT AND FUNCTIONAL 
block diagram for IC1, the Matorota 
UC2BZZ tow-power FM transmitter chip. 

Power consumption is re- 
duced by disabling the audio 
amplifier when the receiver is 
squelched* and it is also kept 
low because U is run from the 
unregulated power supply In 
combination with the 32 -ohm 
speaker. This arrangement 
holds receiver consumption 
down to only 7 milliamperes 
from the battery pack when the 
receiver is in the squelch mode. 
The gain of the audio amplifier 
is set by resistor R29 (between 
pins 4 and 5) and nearby re- 
sistor R24, and is expressed as 
(2 X R29/R24). 

The transmitter Is a 3-watt 
narrow-band FM Class E circuit 
with efficiency greater than 
90% /The front end of the trans- 
mitter is based on !C1 (Fig. I)* 
the low-power FM transmitter 
chip. The voice signal is picked 
up by the microphone and fed to 
thcMin AMPiNPirron pinS of ICL 
Resistor RU (between pins 4 
and 5) sets the gain of the am- 
plifier, and the output of the am- 
plifier drives the FM modulator 

A variable reactance in the 
modulator '^bends' the frequen- 
cy of the crystal-controlled os- 
cillator. Because the crystal 
frequency cannot be deviated by 
more than a few kilohertzby the 
variable reactance circuit, a 
multiplication scheme derives 
the proper carrier and modula- 
tion frequencies. In the E- 



Reslstors (All 1206 SMD chip re- 
sistors are 1/8-watt, 5%, unless 
otherwise specif led) 

Rl— 47 ohms, 1/2-watt. 5%, radial- 
lead 

R2— 22 ohms. 1206, SMD 
ohms/1206, SMD 
R4— 220 ohms. 1206. SMD 
R5— 330 ohms. 1206. SMD 
R6^70 ohms. 1206. SMD 
R7— 1000 ohms, 1206, SMD 
R8, R9— 4700 ohms, 1206, SMD 
RIO— 4.7 megohms. 1206, SMD 
R11, R1 2— 22,000 ohms, 1206 
SMD 

R13, R24— 10.000 ohms. 1206 
SMD 

R14. Rl 5—47.000 ohms. 1206 
SMD 

R16-R23— 100.000 ohms, 1206 
SMD 

R25, R26— 100.00 Ohms potenti- 
ometer, Bourns 51CADD12A20. 
or equivalent 
Ra7— 330.000 Ohms. 1206 SMD 
R28— 390.000 ohms, 1206 SMD 
R29— 680,000 ohms. 1206 SMT 
R30— 510.000 ohms, 1206 SMT 
R31 — current variable resistor, poly- 
mer-based, Raychem Polyswttch 
RXE040 or equivalent 
Capacitors 

CI— 5 pF NPO 805 SMD ceramic, 
Tayio-Yuden UMK212CH0R5D- 
B or equivalent 

C2— 22 pF NPO ceramic disc. 100- 
volt, Panasonic ECC- 
F2A220JCE or equivalent 

03. C4^7 pF NPO 805 SMD ce- 
ramic, Tayio-Yuden UMK- 
212CG470K-B or equivalent 

C5— 56 pF NPO 805 SMD ceramic, 
Tayio-Yuden UMK212CG560K-B 
Of equivalent 

C6-C10— 68 pF NPO 805 SMD ca* 
ramie, Tayio-Yuden UMK- 
212GG680K-B or equivalent 

C11— 82 pF NPO ceramic disc. 100- 
voll, Panasonic ECC- 
F2A820JCE or equivalent 

012— 120 pF NPO 605 SMD ce^ 
ramie. Tayio-Yuden UMK- 
212CGt21K-B or equivalent 

013— 330 pF NPO 805 SMD ce- 
ramic, Tayio-Yuden UMK- 
212CG331K-B Or equivalent 



Comm, a crystal frequency 
equal to one- third of the carrier 
frequency was chosen. Inductor 
L9 (In series with XTAL3 be- 
tween pins 1 and 16 of ICl ) cen- 
ters the oscillator frequency 



C14. C15— 470 pF NPO 805 SMD 
ceramic, Tayio-Yuden UMK- 
212CG471K-B or equivalent 

CI 6. 026. 027— 0.01 M-F Y5V 805 
SMD ceramic, Tayio-Yuden 
UMK212F103Z-B or equivalent 

C17-C23— 1000 pF NPO 805 SMD 
ceramic. Tayio-Yuden 
UMK212SL102K-B or equivalent 

C24— 1500 pF X7R 805 SMD ce- 
ramic, Tayio-Yuden UMK- 
212B152K-B or equivalent 

025, 029, 031^036— 0.1 jjlF Y5V 
805 SMD ceramic, Tayio-Yuden 
UMl^12F104Z-B or equivalem 

C 28— designation not used 

C30—8-50 pF trimmer capacitor, 
Sprague-GM GKG50011 or 
equivalent 

C37-C40, 042. 043. 046— VP 
1206 SMD tantalum. 16-voll 

041 — designation not used 

C44— lO^F electrolytic, 16-volt, 5- 
mm, Panasonic ECE-AICGEIOO 
or equivaJent 

C45— lOOp-F electrolytic, 16-volt. 
6.3 mm, Panasonic ECE- 
A1CGE101 or equivalent 

Semiconductors 

D1, D2— DL4148 switching diode. 
1206 SMD, 

D3— DL4003 silicon rectifier, SMD 

D4— 1N4758A 56-volt Zener diode 

LED1— HLMP-1503-101 (Hewlett- 
Packard) green fight-emitting di- 
ode right-angle indicator or 
equivalent 

Q1, Q2~MPF6660 power FET, 
(Motorola) or equivalent 

101— M02833 (Motorola) tow- 
power FM transmitter system. 
SMD 

102— 74AOL11132 (Texas Inslru- 
menis) quad N AND gate, Schmitt 
trigger. SMD or equivalent 

IC3— MC3363DW (Motorola) low- 
power dual-conversion FM re- 
ceiver, SMD package 

1C4--MC34119 (Motorola) low- 
power audio amplifier, SMD 

105— MAX666CSA (Maxim) vott- 
age regufator. SMD package 

Inductors 

L1-L3--0.33 tLH, adjustable coil, 
Toko. 292KNAS-T10342 or 
equivalent 



when no modulation is applied. 
The buffered output of the os- 
cillator on RE' OUT! 'I ] r pin 14 then 
feeds a lank circuit made up of 
inductor LI and capacitor C8. 
which is tuned to the third har- 



PARTS LIST 



L4, L5— €.68 |iH, axiaMeaded in- 
ductor, Taiyo-Yuden, 
LAL04NAR58M or equivatent 

L6— 1.2 (aH SMD inductor, 2,5 x 
3,2mm or ecjuivalent 

L7— 1.6 ^iH axial-leaded inductor, 
Taiyo-Yuden LAL04NA1R8M or 
equivalent 

L8— 2.7 axial-leaded inductor, 
Taiyo-Yuden LAL04NA2R7M or 
equivalent 

L9— 10 M-H adjustable mductor, 
Toko F292CNS-T1052Z or equiv- 
alent 

UO— quad coil. Toko 5SVLC- 

0637eJT or equivalent 
Switches 

51— OPOT pushbutton switch. 
(Schadow) F2U0A or equivalent 

52— SPDT slide switch, C&K, 
1101M2S3AQE2 or equivalent 

Connectors 

J1— 50-ohm BNC bayonet-style, 
PC- board-mount jack wUh two 
hex ring nuts 

J2— charging jack, Cui Stack 
PJ-002A or equivalent 

J3 to J5— sockets. 2-pin 2mm, Mo- 
fex 53014-0210 with three 2-pin 
plugs, 2mm. Molex 51004-0200 
and six pins, Molex 50011-8100 or 
equivalent 

Crystals 

XTAL1— 37,845-MHz third-over- 
tone crystal. Toyocom, HC-49 or 
equivalent 

XTAL2— 10.245 MHz parallel- 
mode crystal, 32 pR Toyocom. 
HC-49 or equivalent 

XTAL3— 9.0483-MHz parallel- 
mode crystal. 32 pF, Toyocom, 
HG-49 or equivalent 

RItars 

F1 — 455-kHz ceramic filter, Murata 
OF UM455E or equivalent 

F2— lOJ'MHz ceramic filter, Toko 
SK107M5-AO-10 or equivalent 

Other Components 

MIC1— microphone, Panasonic 
WM-54BT or equivalent 

SPKR1— speaker, 2-inch square, 
32-ohm, Regal, SA*200 or equiv- 
alent 

ANT1 — flexible coil antenna with 
BNC bayonet'Style plug. 



monlc or the oscillator. 

The signal Is multiplied by a 
factor or three to obtain the car- 
rier frequency in this tank cir- 
cuit. Both the carrier and the 
modulation stgna! are multi- 



Miscellaneous: PC board, 
custom-made battery pack with 
eight rechargeable nickel-cad- 
mium AA cells. No, 24 AWG wire: 
one 120-volt AC to 12-volt DC 
adapter for charging the power 
pack; custom-made extruded 
case with bottom panel and silk- 
screened top panel; one custom 
made speaker grill; two knobs. 
Keystone, 8580 or equivalent 
with two hex ring nuts each; tour 
No, 440 X 3/8-inch Philips-head 
screws, black: four No. 6-32 X 
Sn6-inch Philips-head screws, 
black; four No. 6-32 intemal*tooth 
lock washers, four No. 6-32 hex 
nuts, one perforated hole plug, 
Hayco 2637 or equivalent; six- 
inch length of shielded wire; 12- 
inch length of No.24 AWG wire; 
fine solder wire; tools and ac- 
cessories as specified in Ihe text. 

NOTE; The following parts are 
available from Micro Advance- 
ment Products^ Inc, RO, Box 
8506, Hollywood, PL 33084 
800-358-8545 

• Printed circuit board only- 
Si 2.00 

• Kh with printed circuit board 
and alt components — $97,00 

• Enclosure including all hard- 
ware, microphone, speaker, 
knobs and transmit button — 
$38.00 

• Battery pack— $17.95 

• AC to DC adapter for charging 
power pack J wall outlet 
mount— S7.85 

• Flexible ' rubber ducky*' 
seven-inch 27-MHz antenna 
with BNC bayonet-style plug — 
S17<95 

• Complete kit for one E-Comm 
tra nscei ver— $1 68.00 

• Complete kit for two E-Comm 
transceivers— 5297.00 

• One E-Comm transceiver as- 
sembled and testetJ— S229.M 

Please add $4,95 for shipping 
and handling to all orders. Free 
frequency modification sheet 
and crystal list with each order. 



plied to obtain tlie 5-kHz devia- 
tion required by the receiver 
Next tlie signal is passed 
through a tuned common-emit- 
ter amplifier to amplify and 
smooth the carrier 



Next the signal is clipped by 
the quad nand Schmitt trigger, 
1C2. a 74AC11132 high-speed 
CMOS logic gale. Two sections 
of 1C2 (IC2-b and IC2-c} provide 
drive to turn a parallel-con- 
nected pair of enhancement- 
Ill ode MPF6660 power 
MOSFETs. Ql and Q2, on and 
off. Class E operation is ob- 
tained with the fast switching 
as well as the low on resistance 
of the power MOSFETs. 

Theoretically, ifno power were 
required by the switch for ac- 
tivation (driver power K and if it 
were lossless, E-Comm would 
be nearly 100% efficient. Al- 
though the FETs do not form a 
perfect switch, they offer several 
useful characteristics: The in- 
put power required to drive the 
PET'S is veiy low (drawn prin- 
cipally in switching the gate in- 
put capacitance on and off at 
high speed (less than 6 nanose- 
conds), and their switching 
speed is very high. 

Those characteristics give the 
transmitter an efficiency of 
about 90%, measured as the 
ratio of rms RF power (delivered 
to the 50-ohm load) to the DC 
supply A five-pole filter matches 




FIG. 4— PINOUT AND FUNCTtONAL 
bloek diagram for the Motorola 
MC3363DW low-power, dual-conversion 
FM receiver chip. 



P 



2 



e 



40 




FIG. 5— PARTS PLACEMENT DIAGRAM tor Iho E-Comm transceiver. Nole radial lead-^ 
ed components C2, C11, R30 and F2, Axial leaded components R1» L4, L5, L7, LB and 
D4 are vertlcaily mounted. 



the output of the MOSFET 
switches to the antenna imped- 
ance while also filtering. 

Variable capacitor C30 fine 
tunes the output stage to match 
the antenna or dummy load. 
Notice that to obtain class E op- 
era t ion, lioth the load and the 
multiplier stages must be tuned 
In accordance with instruc- 
tions in the Calibration and 
Tlmeup section of this article. 
Mismatch and ov^erload protec- 
tion are provided by Zener 
clamp D4 (Fig.L between Ql 
and Q21 as well as the Poly- 
switch protective resistor R31 
(Fig, 2, upper left) in the power 
supply. 

The low- volt age regulator 
shown in Fig, 1 includes a 
CMOS voltage regulator 1C5. a 
Maxim MAX666, which con- 
serv^es power and provides two 
features: low quiescent current 
ofabout 15 microamperes and a 
built-in low-battery detect func- 
tion. The regulated output is set 
by resistor R18 (pin 6) and R28 



to be 6.4 volts. This voltage level 
was chosen to provide enough 
gate voltage lo switch powder 
MOSFETs Ql and Q2 on hard 
without exceeding the max- 
imum voltage specification of 
the quad nand gate IC2. 

The low-battery detect circuit 
Is set by resistors R17 and R30 
at LBi pin 3 of IC5 to about 8 
volts. Because the voltage reg- 
ulator is a CMOS device, high 
resistor ralues are placed in the 
feedback loops for further re- 
duction of power consumption. 
Pin 7 of 1C5 Luo has an open- 
drain output that drives the 
low-battery indicator LEDL 

The receive/transmit switch 
SI -a turns the receive and 
transmit sections of the trans- 
ceiver on and off for further 
power conservation. The power 
pack consists of eight AA nickel- 
cadmium rechargeable cells, 
each with a rating of L2 volts at 
500 milliampere hours. The 
pack is charged through con- 
nector J2 (Fig, I, upper left) by a 



120-voU AC to l2-volt unregu- 
lated DC adapter plugged into 
the AC line. 

Building the txansceiver 

Surface mount devices (SMD) 
were chosen for E-Comm be- 
cause they permit the con- 
struction of a miniature trans- 
ceiver, and their small compo- 
nent dimensions help to keep 
PC board traces short- There- 
fore, by building this trans- 
ceiver you 11 get a leg up on the 
whole process of surface-moun t 
technology (SMT) because you 
will gain iiands-on experience 
in picking and placing the mini- 
ature components and an 
awareness of both the benefhs 
and drawback to SMT However. 
do not attempt to construct this 
transceiver unless you are an 
accomplished project builder 

I^BJisceivcr assembly 

Many SMD coniponents are 
not marked with values or rat- 
ings because of the limited 




RG. e^UTAWAY VIEW OF ASSEMBLED E^omm TRANSCEIVER showing the pos*- 
lions of the controls and the iocations of the microphone, speaker, loaded circurt 
board and power pack. 



space on their cases. This 
means that you must be ex- 
tremely careful to avoid mixing 
up chip components before and 
during construction. 

Specialized tools should be 
used in picking and placing 
SMD components. They should 
be suitable for grasping smalL 
hard~to-handle parts. Recom- 
mended are stainless steel nee- 
dle-point curved-end jewelcr*s 
tweezers for picking and plac- 
ing small parts such as chip re- 
sistors, capacitors and diodes 
on the circuit board. Fine jew- 
elers pliers will be useful for 
straightening stub leads on sur- 
face-mount IC's. 

Do all soldering with a fine- 
tipped 10- to 15-watt pencil-type 
soldering iron. A lighted magni- 
fying glass will be helpfuK pref- 
erably one that mounts on the 
edge of a bench. Use only high- 
quality fine (0,01- to 0.02-inch) 
diameter solder wire and a suit- 
able liquid flux. Keep tine sol- 
der-removing braid on hand lo 
correct any mistakes that you 
might make. 

Anyone building E-Comm 
should be mentally prepared for 
the surprisingly small size of 
the SMD components and their 
close spacing. Working with 
SMD components calls for near 
professional quality soldering 
skills and a lot of patience. Set 
up for building E-Comm on a 
well lighted desk or bench and 
sit in a comfortable chair. Do 
not start this fine work unless 
you are rested and relaxed: mis- 
takes can be costly and frustrate 
ing to correct! 

Refer to the parts placement 
diagram. Fig. 5, Be sure to ob- 
serve all conventions when 
mounting polarized compo- 
nents such as diodes and capac- 
itors. Dots on the PC board 
denote polarity. Position all po- 
larized capacitors so the 
positive lead is nearest the dot, 
and position all diodes and rec- 
tifiers so their cathodes are 
nearest the dot. Be sure to find 
the markers indicating pin 1 on 
all SMD packages. It is typically 
a white dot. 

Do not attempt to build this 
circuit on any PC board except 
one that has been specifieaily 
designed for this circuit. Failure 



to observe this wiH result In a 
poor performing transceiver. A 
proper PC board for RF circuitry 
needs an adequate ground 
plane and short interconnects 
to prevent inadvertant oscilla- 
tions, loss of sensitivity and 
noise- related problems. 

The accurate and effective 
mounting of SMD components 
requires a solder mask on the 
PCB because of the cramped 
lead spacing, A double-sided 
board with plated-through 



holes and solder mask Is avail- 
able from the source given in 
the Parts List, It can be pur- 
chased as a single item or as 
part of the options listed. 

An orderly assembly pro- 
cedure is recommended be- 
cause of the cramped PC board 
layout and the mixture of small 
and large components on the 
board. Solder all surface-mount 
iCs to the board first. This is the 
most time-consuming and te- 
dious part of the project! 




WIRE SIDE of E-Comm transceiver circuit board 



In soldering SMD ICfe. first tin 
one of the comer pads on the PC 
board. Then* with needle-nose 
tweezers* grasp the part and 
center it so the Jeads align with 
all of the pads. Solder the corner 
lead to the pad that has been 
tinned. Next solder the pin diag- 
onally across from the first pin, 
making sure that the case is still 
centered on the pads. Before 
soldering the remaining pins, 
refer to Fig, 5 and verify that the 
IC is In the correct position: 
then double check to be sure 
that pin 1 is in the correct loca- 
tion. 

Be careful not to apply too 
much solder at each pad, and 
try to avoid making inadvertant 
bridges with the molten solder 
between Intended connections 
and adjacent pins. If bridging 
occurs, use a solder-removing 
braid and flux to remove it. Also 
avoid holding the soldering 
pencil at any connection point 



for more than the time requred 
to cause the molten solder to 
flow to prevent overheating the 
component. 

The next step is to position 
and solder all SMD chip capaci- 
tors and resistors. Install all re- 
sistors and capacitors of the 
same value at the same time to 
avoid mixing values I Tin one 
pad of two-terminal compo- 
nents, place the component in 
the correct position, and hold it 
with tweezers while soldering it 
to the tinned pad. Next, solder 
the other end. 

As in soldering the ICs, use 
only as much solder as is neces- 
sary to form a fillet between the 
component and the PC board 
pad. Be sure that the compo- 
nents are positioned flush 
against the board. 

After all SMD components are 
mounted, clean the entire PC 
board with flux removen and in* 
spect all of the soldered connec- 



tions with a magnifying glass. If 
all of the SMD soldering appears 
satisfactor>^, mount all of the 
leaded through-hole compo- 
nents with the exception of in- 
ductor L8 and solder them in 
position, (Inductor LB is to be 
installed after the multiplier 
stages are aligned,) 

l^ke care when soldering the 
connectors because their leads 
are off-centered. The axial-lead- 
ed inductors and resistor Rl are 
mounted through holes. Use 
the sllkscreened pattern on the 
PC board as a guide. Be sure to 
mount the switches and potcn- 
tiometers so they lie flush 
against the PC board. 

Now assemble the battery 
pack, microphone and speaker. 
Assemble the connector plugs 
for J3 to J5 by crimping and 
soldering them to the battery 
pack, microphone and speaker 
wires. Solder two six-inch 
lengths of insulated 26 AWG 
wire to the speaker and twist 
them together. Next solder pins 
to the ends of the speaker wires, 
being careful not to let solder 
flow into contact area. Then 
push the pins into the mating 
plastic plug housing. Each pin 
should snap into place if it is 
assembled correctly. 

The assembly work on the 
battery pack subassembly is 
limited to twisting the wires 
and attaching the connector 
plug. Note that this connector Is 
polarized and can only plug In 
one way. Verify thai the batlery 
connector polarity is correct be- 
cause reversed polarity will de- 
stroy the transceiver! 

Solder a four-inch length of 
shielded coaxial cable to the mi- 
crophone with the shield con- 
nected to the negative side of 
the microphone. Then conned 
the cable to the polarized con- 
nector again observing polarity 

Fasten the microphone into 
the plastic snap-in bushing 
with a room- temperature vul- 
canizing (RTV) silicone adhe- 
sive. Mask the front surface of 
the microphone with masking 
tape to prevent the entry of any 
adijesive in the microphone or 
it could be ruined. Be sure that 
the wire side of the microphone 
is flush with the back of the 
. continued on page 60 



BUILD THIS 

REFLEX TIMER 



' Clf 

#>Off 

o * 



Reflex Timer 




How fast are your reflexes? 

The reflex timer wiU show you. 



DAN KENNEDY 



HOW LONG DOES IT TAKE YOU TO 

dose a switch after you hear a 
buzzer? When driving, how 
long does it take to hit the 
brakes after you see an obsta- 
cle? What we're realty asking is, 
"How quick are your reflexes?" 
Our reflex timer will show you. 

Tfestiog your reflexes is a two- 
person job. To use It. one person 
secretly starts the timer, which 
sounds a buzzer. Upon hearing 
the buzzen the person whose re- 
flexes are being tested turns the 
timer off as fast as he can. (That 
also turns off the buzzen) The 
person s reflex time can then be 
determined by observing a ID- 
LED display 

Figure 1 Is a schematic di- 
agram of the reflex timer, which 
consists of a 555 timer (ICl) and 
three 74LS193 4'bit binary 
counters {IC4^IC6). The 555 
timer outputs a pulse about 
twice ever>^ millisecond, or 2000 
times a second. Tlie timer is se* 



crclly activated by SI which 
then turns on piezo buzzer BZl 
via Ql» and connects the clock 
output from the 555 to the bin- 
ary counters through one nand 
gate (lC3-d), as shown in Fig. 2, 
The person being timed turns 
S2 off, which disconnects the 
555 output from the counters 
and turns off tiie buzzer Quad 
NANO gate IC2 Is configured as 
two separate latches, also as 
shown in Fig. 2, to prevent the 
contacts of SI and S2 from 
bouncing. 

Depending on how long it 
takes the person to shut off the 
timer, a certain number of 
LED*s light up. The numbers 
next to each illuminated LED ( L 
2, 4, 8. 16, 32, etc.) are then 
added together to give the per- 
son's reflex time in millisec- 
onds. If all the LED*s are lit. the 
total elapsed time is 51 1 millise- 
conds or 0.511 seconds. The in- 
dicated time can be multiplied 



by a correction factor to give a 
more precise measurement, but 
that's not necessary for relative 
measurements or "contests'to 
determine who has the fastest 
reflexes. Well talk more about 
the correction factor later. 

A 7805 voltage regulator (IC7) 
provides -r 5-volts DC for the cir- 
cuit from a 9-volt battery. TVvo 
5. IK resistors (R! and R2)anda 
0.047 \lF capacitor (CI) give the 
555 a clock frequency of approx- 
imately 2000 Hz, or 2 cycles per 
millisecond. Tty using a few dif- 
ferent 0,047-(xF capacitors for 
CI to get the frequency as close 
to 200 Hz as possible. Closing 
switch 54 puts C2 (a 47 [lF ca- 
pacitor) in parallel with CI. 
That slows dowTi the timer to 
demonstrate how a binary 
counter works, The numbered 
LEDs will count the number of 
times that LEDl turns on. The 
formula 1440/(R1 + 2R2}C1 
gives the timer frequency in Hz, 



I 

—I 

i 

a 

3 

a' 

z 



43 




FIG. 1— SCHEMATIC OF THE REFLEX TIMER. It consists of a 555 timer and three 

74LS193 4.blt binary counters. ^^^^^ are in kilohms 




and CI is In microfarads. 
Switch S5 lets you turn off the 
buzzer when demonstrating the 
counters with the lower clock 
speed. 

The 74L5193 cotmters 

The 74LS193 is a 4-bit up/ 
down binary^ counter that can 
operate at clock speeds up to 25 
MHz. Data input pins po-P3 
allow a 4-bit binary number to 
be loaded into the counter be- 
fore counting begins. The loaii 
input (Ud, pin 11} must be 
pulsed low to load the 4-bit 
number. Notice thai the data in- 
puts (PO-P3) of all three counters 



RG. 2— QUAD NAND GATE IC2 is configured as two separate latches to prevent the are grounded and that the LOAD 
contacts of S1 and S2 from bouncing. The clock output from the 555 is connected to p 1 ns are held at +5 vol ts 
the binary counters through one gate of IC3. through R4. Momentarily clos- 



10 



11 



12 



13 



14 



15 



16 17 



Era 



00(1) 1 
0U2I 0 
02(41 0 



FIG. 3— WHEN ONE COUNTER RNISHES counting up to 15, it sends a carry pulse to 
the next counter. Here's how a counter responds to 17 clock cycles. 



5V 



RG, 4— THE COUNTERS ADVANCE one count on each low^to-hlgh transition of the 
clock (point "X" on each rising edge). 




RG. S— THE REFLEX TiMER PROTOTYPE was buiit using perforated constructfon 
board and point-to-point wiring. Switches Si and S2 are housed In piastic 35mm fiim 
canisters and connected to the main baaM with three-connector wire. 



ing switch S6 grounds the ld 
pins and sets all three counters 
to zero. Although the clear 
inputs (cl) are permanently 
grounded, pulsing them to +5 
volts would also reset the cir* 
cuit*s counters. 

The COUNT DOWN inputs (dn,, 
pin 4) are held at 4-5 volts 
through R16. The clock signal 
from pin 3 of the 555 is applied 
to pin 5 on the first counten IC4, 



When 1C4 finishes counting up 
to 15 J t sends a carry- pulse from 
its VP, J (pin 12) to the count up 
input (up,, pin 5] of the second 
counter* ICS- Likewise, when 
the second counter reaches a 
count of 15, it sends a carr>^ 
pulse from it upo pin to the third 
counter ICS. Figure 3 shows 
how a counter responds to 17 
clock cycles. A low*to-high tran- 
sition triggers the counter. 



When a counter reaches 15, it 
starts counting again at zero- 
Accuracy 

Figure 4 shows the clock sig- 
nal that is fed to the counters, 
which advance one count on 
each low-to-high transition of 
the clock (point "X" on each ris- 
ing edgej. We can start and stop 
the count anywhere In the clock 
cycle. Suppose we start at Tj 
(just after a low-to-high transi- 
tion); the timer will advance one 
count when T^ is reached, 
which will correctly indicate 0.5 
milliseconds have elapsed, 
Howeven we don't know exactly 
where In the clock cycle the 
timer will be started. Suppose 
the timer is started at T2 and 
stopped at T3. The timer would 
read 0.5 milliseconds more 
than the actual elapsed time be- 
cause the timer started at T2 
and immediately registered one 
count. 

A similar situation occurs at 
the stop time. If we start the 
timer at Tj and stop at T3 the 
count win be correct. But if we 
start the timer at Tj and stop at 
T.|» the timer would read 0.5 
milliseconds less than the actu- 
al elapsed time since we stopped 
the counters just before a low- 
to-high transition. That means 
that the accuracy of our timer is 
limited to ±0*5 milliseconds 
when we use a 2000-Hz clock. 
(That is also plus or minus the 
least significant bit (LSB) of our 
counters, which is the LED 
without a number next to it. 

Another factor that deter- 
mines the accuracy of the refiex 
timer is the clock frequency If 
you have a frequency counter 
you can measure the clock out- 
put from ICl directly If a fre- 
quency counter is not available, 
you can measure the clock fre- 
quency using a stopwatch and 



PARTS LIST 

All resistors are %-watt, 5%. 

R1. R2— 5100 Ohms 

R3— 10,000 ohms 

R4 — 4700 ohms 

R5^R15--470 ohms 

Rt&— 1000 ohms 

Capacitors 

Cl— 0.047 ceramic 

C2 — 47 ^lR 10 volts, electrolytic 

Semiconductors 

ICI— 555 timer 

iC2, 1C3— 74LS00 quad NAND 
gate 

IC4^1Ce— 74LSt93 4-bit binary 

counter 
IC7— LM7805 5-vort regulator 
Q1— 2N3904 NPN transislor 
LED1— LED10— red LED 
LED11— yellow LED 
Other components 
BZ1— PiezD buzzer 
SI, S2— 'SPDT switch with center 

off 

S3-S5— SPST switch 

36— SPST normally-open push- 
button switch 

Miscellaneous: Perforated con- 
struction boardt standoffs, project 
case, IG sockets, wire, sotder, etc. 



the calibration LED {LEDU). If 
the clock frequency is exactly 
2000 Hz. then it would take 
40.96 seconds for LEDIl to 
turn on twenty Limes. The au- 
thor measured 4L5 seconds for 
LEDl 1 to light twenty times. To 
calculate the frequency multi- 
ply 2000 X 40.96/4L5: that 
comes to 1974 Hz. (A frequency 
counter measured it at 1979 
HzJ With a clock frequency of 
less than 2000 Hz. the indicated 
reflex time would be slightly less 
than the actual reflex time. Mul- 
tiplying the indicated time bv a 
factor of 2000/1974, which is 
equal to 1.013, would give the 
reflex time correct to the nearest 
millisecond. 

Construction 

No PC board is required to 
build the reflex timer. Instead 
you can use perforated con- 
struction board and point-to- 
point wiring. The photo in Fig. 
5 shows how the author's pro- 
totype was built and installed in 
a plastic case. 



The author used plastic 
35mm film canisters to house 
switches SI and S2, although 
other mounting schemes can 
certainly be used. Three-con- 
ductor wire must be used to 
connect SI and S2 to the main 
board. 

Its a good idea to mount the 
ICs in sockets. That way you 
can easily exchange the 
74LS193 swith 74LS192'stosee 
how a decade counter works. 
The 74LS192 has the same pin- 
out as the 74 LSI 93 but counts 
only to nine before generating a 
carry pulse and repeating. 
Using those chips, tlie timer 
would display up to 399/2 = 
199.5 in binary-coded decimal 
(BCD). If you wanted to read the 
time directly in milliseconds 
(from BCD) you would have to 
change the clock frequency to 
1000 Hz. 

The reflex timer is sure to be a 
smash hit at your next party — 
with it, you will be able to see for 
yourself who has the absolute 
fastest reflexes. R-E 




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CIRCLE 184 OH ¥BE^ INFORMATION CARD 



THIS MONTH WE COr^INUE 

our PC*baseci test*equip* 
mcnt series by building 
the T1004 digital logic IC 
tester and identifier. It is 
capable of testing 7400, 
5400, and 4000 series 
IC^s. In fact, the T1004 
should be able to test any 
digital IC family that has 
the standard Vec ( + 5V> 
and ground configura- 
tion {Vqq on the upper 
left comer of the IC pack- 
age and ground on the 
lower right). On a 14*pin 
DIP that would mean that 
^cc would be pin 14 and 
ground would be pin 7. 
The T1004 will accept 
14-. 16-, 18-, 20-, 22-, and 
24-pin DIP'S. 

The T1004 performs 
the follourlng tests: THith 
table, positive-going in- 
put threshold, negative- 
going input threshold, 
input hysteresis, output 
source capability under 
load, and an open-collec- 
tor test. Additionally, the 
T1004 predicts (based on 
a best-guess analysis} 
what type of IC you are 
testing (HC, HCT TTL, 
etc.). From now on, youTl 
find grab bags of un- 
know^n lC*s very appeal- 
ing because the T1004 
has a feature that can 
help you identify those 
unknown digital ICs, If 
the IC being tested 
matches any of the IC s al- 
ready in the IC database, 
the T1004 will find and 
display the names of 
those ICs. Running a complete 
test on one or all of those names 
wllL In many cases, provide you 
with a comprehensive picture of 
the IC under test. The T1004 
also lets you add fCs to the 
database. As we expand our IC 
support library we will make up- 
dated files available on the RE- 
BBS (515-293-2283, 
1200/2400, 8N1). 

General operation 

Figure I shows the T1004 
block diagram. The chip-select 
section is driven by the Front 
End section which we dis- 
cussed in detail in our June 



PC-BASED 

TEST BENCH 




The T1004 digital logic IC 
tester and identifier can 
handle 7400-, 5400-, and 
4000'Series ICs. 



STEVE WOLFE 



1992 Issue: It selects and de- 
selects every other section In 
the T10D4. The reference-volt- 
age section provides a 2.5-vo!t 
reference for the analog-to-dig- 
itaJ converter (ADC) section and 
also for the digital-to-analog 
converter (DAC) section. The 
pull-up or pull-down section 
(PUPD) is capable of providing a 
10-kilohm pull-up or a 200-ohm 
pull-down to any or all of the 
test-socket pins 1 except the V^^, 
pin). 

The DAC section produces a 
voltage (in 20-milHvolt steps be- 
tween 0 and 5 volts) which is fed 
to the DAC multiplexer {MUX) 



section. The DAC MUX 
can apply the DAC voltage 
to one of pins 1 through 
23 of the zero insertion 
force (ZIF) test socket. 
The DAC multiplexer can 
also disconnect the DAC 
voltage from the test 
socket. The ADC multi- 
plexer can select a single 
voltage from one of pins 1 
through 24 of the test 
socket and feed that volt- 
age to the input of the 
ADC section. The socket- 
ground section supplies 
ground to one of six test- 
socket pins [pins 7— 12) to 
connect the ground pin of 
the IC under test to 
ground. 

Ibsts performed 

• 'Huth-table test 

During this descrip- 
tion well use a 7432 quad 
2-input OB gate as an ex- 
ample device. Because 
the 7432 is a 14-pin de- 
vice, the socket-ground 
section grounds pin 7 of 
the test socket. The DAC 
section is disconnected 
from the socket. The de- 
vice is looked up in the 
database and an input/ 
output (I/O) mask is 
stored as three variables 
(or three 8-bit bytes). The 
I/O mask differentiates 
inputs from outputs* 
During subsequent test- 
ing, the I/O mask protects 
outputs from being inad- 
vertendy grounded. Next, 
a line of the truth table is 
read into the three variables 
from the data base. The 
portions of those three variables 
which correspond to inputs are 
sent to the IC under test via the 
PUPD section. 

At this point the ADC multi- 
plexer and ADC sections scan 
every test socket pin for the re- 
sultant voltage. Voltages found 
to be greater than 2.4 volts are 
converted to highs, and those 
less than 2.4 volts are converted 
to lows. The highs and lows are 
converted to three 8-bit bytes 
that are compared to the bytes 
that were read in from the truth 
table. If they match, the IC has 



i 

m 

a 



47 



TOOACSlCltON 



VOLTAGE 
SECTION 



TO THE 
FRQHT 
EUO 

TO 
EVEHV 
SECTION 



DATA BUS 



t 



CHEP 
SCLECT 
SECTlOfJ 



PULL UP OR 
PULL WWi 



DAC MUX 



TO 23 21^ 
SOCKHPINS 



TO Om OF S3 
ZIF-SOCKET 
PINS 



DAC 



ADC MUX 



]4- 



FR(miON£OFa4 
3F'S0CKET 
PJNS 



ADC 



SOCKET GROUND 



TO ZIF^SOCKET 
PIN 7.8,9.10,1 1, 
OR 12 



HQ. 1— 11004 BLOCK DIAGRAM. The Front End drives the chl(>-select seclioa, which 
selects and deselects ev^ry other section in the T1004. 



passed the first line of the truth 
table, 

• Low-to-high input teat 

In this section three bytes are 
again sent to the test socket. 
The bytes are selected based on 
the following criteria: A kno\ra 
input pin on the IC under test is 
being held low. Additionally, 
when the pin being held low is 
taken high, a known output pin 
will change state. Working to- 
gether, the DAC and DAC muUi- 
plexer sections take control of 
the input pin and slowly ramp 
its voltage from zero to the volt- 
age level needed to cause the 
output pin to toggle. The volt- 
age on the input pin is then 
read back and displayed on- 
screen ne.xt to the label **VT + 

• High-to-low input test 

In this section three bytes are 
gj again sent to the test socket. 
§ The bytes are selected based on 

the following criteria: A known 
o input pin on the IC under test is 
E being held high. Additionally, 
g when the pin being held high is 
z taken low, a known output pin 
8 will change state. The DAC and 
2 DAC multiplexer sections take 
f control of the input pin and 
uj slowly ramp its voltage from +5 

volts to the voltage level needed 
46 to cause the output pin to tog- 



gle. The voltage on the input pin 
is then read back and displayed 
next to the label "VT-:/" 

• Hysteresis 

Input hysteresis is the dif- 
ference between the trigger 
point of an input being taken 
high and the trigger point of the 
same input when it is taken low. 
ICs such as a 7414 intentionally 
have a large amount of hys- 
teresis to give them increased 
noise Immunity. The T1004 cal- 
culates the hysteresis and dis- 
plays it on the screen next to the 
label "HYS:." The T1004 calcu- 
lates hysteresis as follows: 
IVT + ) - [VT-) = (Hysteresis) 

• TTL inpiit compatibility 

A TFL-compatible input must 
trigger when fed a voltage not 
larger than 2A volts. If VT+ Is 
greater than 2.4 volts then the 
IC under test fails the test. 

• Output-load test 

The output-load test is per- 
formed by taking an output 
high and loading it with 200 
ohms to ground for a very brief 
period. During the time that the 
load Is present, the ADC reads 
the loaded voltage. This test will 
reveal weak or damaged gates, 
help to identify the gate type, 
and test for an open-collector 
condition. 



Any of the tests described 
above may be omitted from the 
testing procedure. The testing 
process is defined by a script, 
which is a set of test instrtic- 
tions for a parlictjlar IC, Each 
IC has lis own script which TSW 
or the end user writes to suit a 
particular IC. IC scripts are 
compiled using a program sup- 
plied by TSW. 

Script tutorial 

IC's not presently supported 
by the T1004 can be added to 
the existing database by the 
user. Each script contains the 
IC's name, whether the IC is an 
open-collector device, and Its 
truth - table in format ion . 
Scripts can be written using 
any ASCII text editor. 

The easiest way to create a 
new script is to copy an existing 
script and edit it as needed. 
Once a script has been created, 
it can be compiled and added to 
the appropriate database. You 
can compile a script simply by 
selecting that option from the 
software menu. You will be 
asked to give the name of the 
script (example: S7400.TSW). 
The compiler will then open the 
script and get the IC name* 
Next, it checks to see if the tar- 
get iC already exists in the 
database. If it already exists, 
then the preiious version of the 
IC script will not be overwritten- 

The delete function lets you 
remove any IC from the 
database. If the target IC docs 
not exist In the database, then 
the compiler will compile the 
target script file and add the re- 
sults to the database. The origi- 
nal script is written in a form 
that is easy for a person to fol- 
low. Once compiled, the script 
takes on a more compact form 
that can be used by the main 
testing program. Scripts for 14- 
pin iC's must be located in the 
directory ^TSWMCTEST- 
\D14\SCR1PTS," Similarly, 
scripts for 20-pin IC's must be 
located in the directory 
' \TSWMCTEST\D20\SCRIPTS , ' 
and so on. 

Tkke a look at Listing L The 
top line (TUTORIAL SCRIPT 
NUMBER 1) and the numbers 
down the left side [1-14] are not 
part of the script file. They have 



been added for reference onJy; 
and should not appear in 
serfpts that you write. 

The s>'Tnbols in the beginning 
of each line tell the software 
what kind of function is to be 
performed. A ' tells the soft- 
ware that the two following vari- 
ables are the ICs name and 
whether or not it is an open- 
collector device, respectively, A 
■ tells the software that the 
letters *f." "O, ' 'V/* and "G" des- 
ignate inputs* outputs. Vq^^ 
and ground* respectively "V" 
and "G" always represent V^^ 
and ground* respectively. The 
numbers " 1 " and "0" always rep- 
reseni a logic high and a logic 
low. respectively 

An tells the sofJware that 
following symbols designate the 
truth table of the IC under test, 
and that the data should be sent 
and the results should be read 
back. A ' indicates that the 
following symbols designate the 
truth table of the IC imder test, 
and that the data should be sent 
but not read back* A 7" tells the 
software that the following sym- 
bols designate the truth table 
used for the "low- to-high input 
threshold test" of the IC under 
test, A T says that the two 
following numeric variables 
designate the *'low-to-hlgh In* 
put threshold test" Input and 
output pins* respectively, A "\" 
Indicates that the following 
symbols designate the truth ta- 
ble used for the "high- to-low in- 
put threshold test" of the IC 
under test. A"-" means that the 
following symbols designate the 
truth table used for the "output 
load test" of the IC under test. 
An " = " means that the follow- 
ing numeric variable designates 
the "output load test" output 
pin. 

Lets take a closer look at the 
script in Listing L Line ( I) must 
contain three string variables 
separated by commas. The first 
variable in the line must be a " ?" 
which tells the software that the 
next character Is the name of 
the IC . The IC name can contain 
nine characters* In this case the 
name is "7400/* The next 
character on line (1) tells the 
software whether or not the IC 
being tested is an open -collector 
part: **T* for open-collector parts 



or "N" for parts without an open 
collector. 

Line (2) represents the pin 
numbers of the IC being 
scripted. In this case the IC is a 
14-pin package. Line (3) is the 
first line of the truth-table sec- 
tion* From that line the test 
software is able to determine 
whether to treat any given pin 
as an input or as an output. The 
line must be correct for the lines 
that follow to work correctly. If 
the IC being scripted has more 
than one input/output mode |a 



USTING 1 
TUTORIAL SCRIPT NUMBER 1 



IC KAKE 



CD ?,7400,» 



vtn mmzns 
{2\ oooooooooiiixi 

12345678 901234 



KftlK TRUTH TABLE 



[1) |,I,I,0,I,I,0,C,O,I,I,O,E,I,V 

(4) %O,0,l,O,O,l,G, 1,0,0, 1,0, Q,V 

(5J %0,l,l,Orl,l.G,l,0,l,l,0,l,V 

[7) •aa*o.i*iiO,G,o,ia,o,i,i.v 



TO BIGS IKPtlT TBST 



(8) /,l,0,l,l,0,i,<3,l*l.<»*l,lrO,V 
(9J lt2,3 



HIGH TO LOW IKptrr TEST 

(lOj \,l,l,0a*l,O,<3,O,l,t,0,t,l,V 
(11 J UZrl 



OUTPUT LOAD TEST 



(12) -,0,0,l,O,O,l,G,l,0,0^ 1,0,O^V 



(Hi TSW ELECTftOMICS 

14 I- IK IC TEST SCniKT 



74245, for example), you 
should give a new line just 
prior to the IC's mode change. 
You can use as many lines 
as needed, and you can use 
them in any section of the 
script. In this case pin 1 is an 
input, pin 2 is an input, and pin 
3 is an output* Pins 4-6 follow 
the same pattern and pin 7 is 
ground. Pin 8 is an output, pin 
9 is an input, and pin 10 is an 
input. Pins 11-13 follow the 
same pattern and pin 14 is V^^. 
If you check your data book you 
will see that this accurately de- 
scribes the I/O of a 7400, 



Line (4) begins with an 
That means that any *l"s and 
"0"s corresponding to inputs 
should be sent to the IC and 
that the "Ts and "0"s corre- 
sponding to outputs should be 
read back from the IC. If the"l "s 
and "0"s read back do not match 
the those predicted by the script 
then a fail condition exists, A 
7400 is a quad 2-tnput nand 
gate. The line tests all four gates 
at the same time. In line (4), 
pins 1. 2, 4, 5, 9. 10, 12, and 13 
are all taken low. Each function- 
ing NAND gate must respond by 
outputting a high. The results 
are read back and compared to 
the script. (Any error within the 
script will cause good IC s to fall 
the test). Lines [5) through (7) 
send and test the remaining 
truth* table conditions. An 
can be used only in the truth- 
table section. Within that sec- 
tion, you can use as many 
tines as you like. 

Line (8) begins with a "7.'' 
That character causes the "low- 
to-high input test" (LHT} to be 
performed. The LHT Is used to 
determine the voKage that an 
Input considers a high, or log- 
ical. The "l"s and '*0*s corre- 
sponding to inputs are sent to 
the IC. Line (9) contains the 
character which precedes 
the input and output pins to be 
used during the test. In this ex- 
ample pin 2 is used as the input 
and pin 3 is used as the output. 
When pin 2 is taken from low to 
high, pin 3 changes state- It is 
not important whether pin 3 
goes from high to low or low to 
high* but only that a change of 
state occurs. The T1004 In- 
creases the voltage present at 
pin 2 (in 20-mlllivolt steps) until 
pin 3 changes states. The volt- 
age on pin 2 Is read back and 
displayed. 

Lines ( 10) and [11) contain the 
character and "L" They work 
in the same way except that the 
input voltage is swept from high 
to low. This test Is used to deter- 
mine VT-. Line (12) contains 
the character That sends a 
truth table that must produce a 
high on one of the outputs. The 
next line contains the character 
which tells the software 
which output pin is presently 
high. We could have chosen any 



one of four outputs since tliey 
are all high. In this instance pin 
3 Is chosen, and loaded with 
200 ohms to ground. The load 
test determines the sourcingca- 
pabiUties of the gate, whether 
the part is open-collector or not. 
and provides clues that the soft- 
ware uses to predict the ICs 
family. The predicUon of family 
or type should be considered a 
best guess (not absolute). Line 
(141 contains the text * TSW 
ELECTRONICS," which is there 
as an end-of-file marker for the 
compiler. 

Listing 2 shows ^'TUTORIAL 
SCRIPT NUMBER 2/^ Line (1) 
indicates that the device is a 
4040 and that it is not an open* 
collector device. Line (2) indi- 
cates that a 4040 is a 16-pin de- 
vice, A 4040 is a 12-bit ripple 
counten Line [3) indicates that 
pins 1—7 are outputs, pin 8 is 
ground, pin 9 is an output, pins 
10 and 11 are inputs, pins 12-15 
are outputs, and pin 16 is Vex:* 
Pin 10 is a falling-edge triggered 
clock input. Pin 11 is used to 
reset the counter, and is active 
only when high. Line (4) intro- 
duces the ''% ■ command, which 
is similar to the command, 
except that no test is performed; 

should be used whenever 
you wish to send a byte to the IC 
without testing for a result. 

In line (4) the reskt line (pin 
11) and CLOCK line (pin 10) are 
taken high. On that same line 
all of the outputs arc shown low, 
which is an accurate represen- 
tation of the effect that a reset 
would have on the outputs. Be- 
cause line (4) is a *' % ' line, we do 
not actually test the outputs. 
On line (51 the reset line is re- 
leased. On line {61 the clock Is 
taken low activating the first 
output line (qoK Because line (6) 
uses an Instead of a the 
outputs win be tested for ac- 
curacy. The command al- 
lows you to configure a device 
before you begin to test it. It can 
be used in any section and as 
often as you like. In the low- to- 
high Input test, it Is used to rec- 
onfigure the 4040 before we 
sweep the Input. In this case, 
we are using the reset input to 
determine the low-to-high 
threshold (VT-F). 

The only pin that could be 



used for the high- to-low input 
test is the cloc k pin. Because 
clock input pins require fast 
transition times, they are not 
suitable for use In threshold 
tests. For that reason, the high- 
to-low input test is omitted for 
the 4040 IC- You can omit any 
section except the section 
and the TSW ELECTRONICS" 
section, A must precede 
truth-table, threshold, or out- 
put-load tests. It must appear at 
least once or as often as needed. 



LISTING 2 
TUTORIAL SCRIPT NUMBER 2 



I C Mm 



(21 0 000000001111111 
13345C?a^ai33l5fi 



KAII* TSOTH TABLE 



(31 I^O,O,O,O#O,O^0,C,0,I,I,0,0iO|O,V 

(il %,o,o,o,o,o,o,Q,<:,o,i,irDpOtO,o,v 

{5} %,O,O,O,O,0,Op0rC,0,l,O,O,O,O,O,V 

(fiJ •,0,0,0,0,0,0,0,0, l,0>O,O,O,O,O,V 

(7 J *,B,0,0,0,0,O,O,<;, 1,1, 0,0, 0,0,0, V 

(Sj •,o,o,o,o,o,o,i,c,a*o,o,o,o,o,o,v 

(9 J •,0,0,0,0,D,O,l,C,O,l,0,O,0tOrO,V 

(10 J *,O,O,O,O,O,0,1,C,1,O,O,O,O,O,O,V 

(llj ',0,0,0,0,0,0, 1,0, 1,1,0, 0,0, OrO,V 

(laj •,O,0,0,O,0,l,0,G,O,Q,0,O,0,0,O,V 

(13 J 0, 0, 0, 0, 0,1,0,0,0, I, o,o,o,o,o,v 

(141 •,O,a,0,0,O,l,O,G,l,0,0,fl,0,0,O,V 

(15 J •,0,0,0,0,0, 1,0,G,1, 1,0, 0,0,0,0,V 

(16J •,O,0,O,0,0,l,l,G|0,0,O,O,0,0,0,V 

(171 •,0,O,0,0,0,l,l,O,0,l,0,O,0,0,0,V 

(lei •,o,o,o,o,o,i,i,o,i,o,o,o,o,o,o,v 

(lij -,0,0,0,0,0,1,1,0, 1,1,0, 0,0, o,o,v 



Um TO HIGH INPUT TESt 



(20 J l,O,O,O,O,Or0,O|tJ,O,l,l,O,O,O,O,V 

(21) t, 0, 0, 0, 0,0,0,0,0,0, I, o,o,o,o,o,v 

ill] /, 0, 0, 0,0, 0, 0, 0, 0, 1,0, 0,0, 0,0,0, ¥ 

f23J 1,11,? 



QUTFTIT LOAD TEST 



(241 1,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,7 
{251 %,O,O,0,0,O,0,0,O,0,l,0,0,0,O,O,V 
(261 -,0,0,0,0,0,0,0,0, 1,0, 0,0, 0,0,0, V 
(271 -,9 



(2B} TStr BLECStONlCB 

Ifi PIl JC TEST SCRIPT 



Detailed operation 

We will use BASIC as an exam- 
ple language. As wcVe seen with 
previous peripherals, the first 
step in controIUnii the T1004 is 
to establish a base address and 
select the desired peripheral. 
The first bit of code will be: 
BAS-768 : OUT BAS + 31,4 
768 (hex 3001 Is the factoiy-pre* 
set base address of the 1 1000, As 
noted earlier, this address is 



DIP-switch selectable. Next, we 
have an **OUT TO BAS + 31 / As 
you may recalL that address is 
reserved for peripheral selec- 
tion. The T1004 has a unit, or 
peripheral address of "4." Con- 
sequently, if we send an "OUT 
TO BAS + 31 ^ with a data byte of 
"4/* the T1004 will be readied 
for full I/O operation. 

The T1004 schematic has 
been split into two lialves and 
shown in Figs, 2 and 3, Address 
lines Ao^Ai (32 bytes) are used 
by the T1004 (or any other pe- 
ripheral! to address its IC's, and 
AO is the LSB of the address 
lines, (Lines as-ao are used by 
the 11000 only) The chip*select 
section shown in Fig. 2 
(IC23-IC25) contains two 
74HCT138's (1C23 and 1C241 
Whenever their c2a and g2B 
lines are low and gi Is high, one 
of eight outputs will go low de- 
pending on the address present 
on the A. H. and c inputs. IC23 is 
active when \i\-:N is high» send is 
low, and rd is low IC24 is active 
when BEN is high, send is low, 
and vvR is low All but one of 
1C24S output lines drive the 
load line of the 74HCT573 
latches. Because the load line of 
a 74HCT573 must see a high to 
store data, IC25 inverts the ac- 
tive lows produced by IC24. 

The voltage-reference section, 
also in Fig, 2, is composed of 
IC26, R21, Rl. IC9-a. and ICS b. 
IVimmerRSl Is adjusted for 2,5 
volts at TPL That provides the 
ADC section with a precise ref- 
erence voltage. The reference 
voltage also passes through IC9- 
b and used bv the DAC section. 

An ' OUT TO BAS + 7 ' will load 
a data byte into IC15 (a latch). 
DAC IC16, in combination with 
IC17-a, will produce between 0 
and 5 volts which is propor- 
tional to the byte stored in IC15, 
The voltage produced will be a 
function of n x (5/255), where n 
Is equal to the number loaded 
into thelatch(lC15). ASOO-ohm 
potentiometer (R22) is used to 
set the full-scale output voltage. 
If IC15 contains a value of 255, 
then R22 should be adjusted for 
5 volts at IC17-a pin 1, The DAC 
multiplexer section is com- 
posed of IC18 through IC22. A 
latch IIC18) used to hold the 
DAC multiplexer address. The 




FIG. 2— Ifst THIS PORTION of the T1004 schemallc, address lines A0-A4 are used to 
address IC's, 



least Significant three bits of the 
address are fed to each of three 
8-bit multiplexers 
{74HCT4051). The remaining 
data Unes are fed to IC19 (a 



74HCT138). which activates 
only one of the multiplexer IC's 
(IC20-IC22). Assuming that the 
address byte sent to IC18 was 
less than 23, the DAC voltage Is 



then passed through to the test 
socket. If the address byte is 23 
or greater, then the DAC voltage 
is disconnected from the test 
socket. 





3 




4 




-A 




1; 


* 

OS 


J 


■ 


• 


0? 


9 






4 * * -tj **SVfCT 


















IS J 


t 



RG, 3^THE PULL UP OR PULL DOWN section pulls any or all of the test socket pins 
high or low as needed. 



Latch ICIO is used to hold the 
ADC multiplexer address* The 
least-significant three bits of 
the address arc fed to each of 
three 8-bit multiplexers. The re- 
maining data lines are fed to 
ICll, a 74HCT138. which acti- 
vates only one of the multiplexer 
IC s (IC12-IC14K Assuming that 
the address byte sent to ICIO 
was less than 24, the ADC re- 
ceives voltage from only one of 
the test socket pins. If the ad- 
dress byte is 24 or greater, then 
the ADC is disconnected from 
the test socket. 

The pull up or pull down 
(PUPDl section, shown in Fig. 3, 
Is composed of ICl, ICS. IC6. 
RIO, Rll. R13-R16. R17-R19, 
and 915-Q29. This sec- 
tion pulls any or all of the test 
socket pins high or low as 
needed. The PUPD section Is 
primarily responsible for truth- 
table functions. Three bytes are 
used to control the PUPD sec- 
tion. Byte-A controls test socket 
pins 1— 8» Bytc-B controls pins 
9-16, and Byte-C controls pin^ , 
17-23. Pin 24 Is reserved for 
Vcc only and is not affected by 
the PUPD or DAC sections. The 
sections controlled by Byte-A, 
Byte-B, and Byte-C are func- 
tionally identicaL so well de- 
scribe the Byte-A section only 

Well assume that the number 
85 (01010101) has been sent to 
ICL The OUTPUT enable line on 
ICl (oe) is grounded so the 'Q" 
outputs must follow the "D" in- 
puts. Pin 1 of DIP RIO will re- 
ceive a high, ptn 2 a low, pin 3 a 
high, and so on. Resultantly 
the base of Ql will be taken high 
connecting ground to Rll pin W * 
That causes pin 1 of the test 
socket to be pulled low through 
200 ohms. Because the base of 
Q2 is low. it will not conduct. 
That allows Rl 7 pin 3 to pull Rl 1 
pin 2, and subsequently the test 
socket ptn 2, high. 

The IC ground section con- 
sists of IC2-1C4, R12, and 
Q9-Q14. Any byte latched into 
IC2 is passed directly to IC3, 
Byte values ranging from 0 to 5 
transition to a low one of lC3s 
output lines. IC4 Inverts the 
signals which are then fed 
through R12 to the bases of 
Q9-Q14. Only one line is active 
at a time, thus ensuring that 



only one transistor is con- 
ducting at any given moment. 
Transistor Q9 is selected when 
driving a 14- pin device and Q14 
would be used when driving a 
24-pln device. 

Regulator IC27 and its associ- 
ated components produce - 5 
volt5» which is used by the DAC 
(1C16K Regulator IC28 and its 
associated components pro- 
duce - 5 volts for the multiplex- 
ers (IC12-IC14 and IC20-IC22K 
Regulator IC29 and its associ- 
ated components produce +7 
volts, whicti the op-amps re- 
quire in order to produce a full 
5-voll output swing. Regulator 
IC31 and its associated compo- 
nents produce + 5 voUs for the 
IC being tested. Regulator 1C30 
and IC32 and their associated 



HEATSINK 



components produce +5 volts 
for all the remaining IC's. Reg- 
ulator IC31 produces +5 volts 
and is dedicated to supplying 
Vcc to fhe test socket and +5 
volts to the pull-up resistors 
R17-R19, 

Constructioii 

To build the T1004 pe- 
ripheral, a PC board is recom- 
mended. You can either buy a 
PC board from the source men- 
tioned in the Parts List or make 
your own from the foil patterns 
weVe provided. Note that the 
parts for the Front End are con- 
talned on the T1004 board 
shown with a dark line around 
them in the Parts-Placement di- 
agram of Fig, 4. There is a sepa- 
rate Parts List for the Front 



FRONT inO 



End* which was discussed in 
detail in the June issue. Do not 
confuse the two lists of parts, or 
where they go on the board. 
Also, for many of the capacitors, 
notice that there are three holes 
on the board, with two of them 
electrically the same. The holes 
accommodate capacitors with 
different lead spacing. Use 
whichever pair of holes on the 
prlnied-circuit board that best 
fits the capacitors you intend to 
use for the project. 

One of the voltage regulators 
{IC32) is in a TO-3 case that 
must be mounted on the back 
panel of the T1004 case. Mount 
the regulator, along with an ap- 
propriate heatsink, on the back 
panel and hardwire it to the 
board. Figure 5 shows the com- 




*_JHL_ fl6 = ^ ■ 'Z 

I fm t f 1 r' " 1 I : 1 , r 









c 







TPlO O 

to ^ & 

R2 

1 



IC15 



"ICS 



10^^[:iiOo,e,opooDo 

3 OOOOOD""^ 



0 



1 0 

Q1 




1 023 





C 


1 






1C10 


C 






















IC12; 






IC13; 




iDt4; 












ad, 



IC31 *^ 



24 22 20 IS 1& UXy 



ODD 



1 2 4 e B 10 12 




TOZIFSOCKHPINS 

FIG, 4— PARTS-PLACEWENT DIAGRAM. The parts for the Front End are shown with a 
dark Una around them. There is a separate Parts List for the Front End, so don't 
confuse the two lists of parts, or where they go on the board. 



TO ZIF SOCKET PINS 



I 

63 




T1004 COMPOKEhfT SIDE. 



T1004 SOLDER SIDE 



T1004 PARTS UST 



z 

UJ 



54 



All resistors am vv-watt, 5%, ynfess 

otherwise noted, 
R1— 2200 ohms 
R2— 10,000 ohms 
R3— 2320 ohms, 1% 
R4— 1000 ohms 
R5— 51 10 ohms. 1% 
R6— 2050 ohms. 1% 
R8— 1100 ohms 
R9— 240 ohms 

RIO. R12, R13, RlS-1000ohms. 16-pin 
DIP 

R11. R14, R16— 200 ohms, 16-pin DIP 
R17-R20— 10.000 ohms. 10-pin SIP 
R21— 10*000 ohms, multiturn trimmer 

potentiometer 
R22— 500 ohms, multitum trimmer 

potentiometer 
Capacrtors 

Cl*-€7, ClO-Ct4, Cie-C25, C48— 0.1 5 

|iF, potyslyrene 
C8. CI 6. C31. C35. C37, C39, 042. 

C45— 100 ilR etedfolytic 
C9, CI 5, 020. 032, 033, 034— not 

used 

017, C2A 036, C38, C40, C41, C43. 

C44. C46. C47— 10 jiF. electrolytic 
Cafr—ISO pR mica 

picted T1004 board. When you 
use the T1004, position the ICs 
you want to test as shown in 
Fig. 6. 



029—2,2 fiF, electrolytic 
C30— 36 pF. mica 
Semiconductors 

101, IC2. ICS. 106. IC7. ICIO. 1015, 

IGie— 74HCT573 octal latch 
IC3. IC11, tClS. IC23. JC24— 74HCTl3a 

demultiplexer 
104. 1025— 74HCT540 octal buffer 
ICe— ADC0803 8-bit A'D converter 
!C9— L1\435Q dual op-amp 
!012^IC14, IC20-I022"-74HCT4051 6- 

bW multiplexer 
ICIfi^DACOaOO or DAC08 D/A 

converter 
1017— UVI621 BAN op-amp 
1026— LM336 voltage reference 
IC27, 1028— 79L05 voltage regulator 
1029— LM317T voltage regulator 
IC30, IC31—Uy!7©05T voltage regulator 
1032— UA7805K voltage regulator 

(TO-S case) 
D1— 1N4002 diode 
02 1N5231 5.1-volt Zener diode 
Q1-Q29--PN2222 NPN Iransistor 
Miscellaneousr 24-pin ZtF socket* 

TO-220 heatsink. 10-3 heatsink, PC 

board, instrument case, wire, solder, 

etc. 



Software 

Each peripheral has its own 
software program to control its 
operation. All of the programs 




PIG* 5— THE COM PLETED T1004. One of 
the voltage regulators. 1032, must be 
mounted on the back panel of the T1004 
case. 

end up in one directory as you 
add more peripherals. Software 
for the 1 1000 and the entire sc- 
ries of peripherals, including 
the T1004, can be downloaded 
from the RE-BBS 
(516-293-2283. 1200/2400, 
8N1) as a self-unarchiving zip 
file called T1004,EXE. Both 
compiled and uncomplled soft- 
ware is included. Software is in- 
eluded free with the purchase of 
any peripheral from the source 
that is mentioned in the Parts 



THE Tim AimfS OOHHECTS 
Vq. (+5 mis DC) TO THIS PIN. 



i 



PIHt(OfTKElWTEaRArED 
CiRCytT Biim TtSTED) MUST 
BE LOCATED HERE. 




CORRECT POSlTlONlNtS 




tNCORREQT POSmONING 



FfG. 6— BE SURE TO POSITION the IC's you want to test In the test socket as shown 
here. 



FRONT'END 

Resistors 

R1™33 ohms. 16-pin DIP nesrstor 
R2— 2200 ohms, 10*pin SIP fosistor 
R3— 1000 ohms. lOiHn SIP resistor 
Capacitors 

Ct-C7— 0J5 |jlF, 50 volts, monofythic or 
polystyrene 

C8-C11. C20-<;2e-^1500 pF. 63 volts, 
polystyrene 

C12-C19— 220 pF, 100 volts, ceramic 
dtsc 

Semiconductors 
iCI— 74LS573D octal latch 
IC2— 74LS688D 8-fait magnitude com- 
parator 

1C3— 74LS245D octal transceiver 

JC4— 74LS02D quad 24nput NOR gate 

[C5, IC6— octal buffer 

IC7— 74LS08D quad 2-input AND gale 

Other components 

J1 — 16-pin male header 

J2 — 18*pin male header 

J3 — male PC- mount OS25 connector 

Miscellaneous: 17 shorting b[ocks (for 
J1 and J2) 

Note: The following items are avail- 
able from TSW Electronics Corp., 
2756 N. University Drive. Suite 166, 
Sunrise, FL 33322 (305) 748-3387: 

• HOOO kit— $65.00 

« hOOO PC board only^$35.00 

• 11000, assembled and tested— 
S77.00 



List- (Software can also be pur* 
chased from that same supplier 
If you Ye not buying anything 
else from them and you have no 



PARTS LIST 

• 6-foot interfac«} cable (DB-26^>— 
$12.95 

m T1001 kit (includes PC beard, all 
listed parts, project case, and p re- 
assembled front and rear panels— 
$149.00 

• T1001 PC board only^9.00 

• T^OOI, assembled and tested— 
S179.00 

• T1001 software {included free with 
T1001 order)^S10.00 

• Capacitor kit (unmeasured) — 
S21.00 

« Capacitor kit (measured to within 
1%)— $26.00 

• T1003 kit (includes PC board, all 
listed parts, project case, and pre- 
assembled front and rear panels) — 
SI 59.00 

• T1003 PC board only— ^59.00 

• T1003. assembled and tested — 
$189.00 

• T1003 software (Included free with 
T1003 order)— S10.OO 

• T1004 kit (Includes PC board, all 
listed parts* protect case* snd pre- 
assembled front and rear panels] — 
S209.00 

• T1004 PC board only— S79,00 

• T1004, assembled and tested- 
$249.00 

• T1004 software {included free with 
Tt004 order)— $10.00 

Add $5.00 S & H to any order. Check or 
money order only. 

way of downloading it from the 
RE-BBS.) With the T1004. you 
are on your way to automatic 
troubleshooting, r-e 




Earn Your B.S. Degree 
in 

ELECTRONICS 
or 

COMPUTERS 



By Studying at Home 

Grantham College of Engineering, 
now in our 42nd year, is highly ex- 
perienced in **disiance education" — 
teaching by correspondence- through 
printed materials, computer materials, 
fax, and phone. 

No commuting to class. Study at 
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lesson materials, with additional help 
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Our Computer B,S. Degree Pro- 
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An important part of being pre- 
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Write or phone for our free 
catalog. Toll free, 1-800-955-2527, or 
see mailing address below. 



Accredited by 
the Accreditmj* Commi^^ion of the 
Noltoiial Hnnic Study Council 



GRANTHAM 

College of Engineering 

Grantham College Road 
SUdell, LA 70460 



m 

B 

% 



59 




HAINDi TALKIE 



cominued from page 42 



bushing to provide a gap be- 
tween the top of the m icrophone 
and the holes in the face of the 
bushing, (that permits sound to 
enter unimpeded.) 

It is recommended that the 
bushing be snapped Into the ex- 
trusion before performing the 
microphone bonding step or the 
plastic snaps will interfere with 
the microphone. 

Refer to the mechanical 
layout drawing Fig. 6 as a guide 
for mechanical assembly. At- 
tach the front panel to the PC 
board. First attach hex ring 
nuts to the front of both 
SQUELCH potentiometer R25 
and VOLUME potentiometer R26, 
and coaxial BNC connector Jl. 
Be sure that the PC board abuts 
the front panel and is fastened 
with hex ring nuts on the out- 
side of the threaded barrels of 
the potentiometers and BNC 
connector Avoid placing exces- 
sive torque on the potentiome- 
ters by holding the hex ring 
nuts behind the panel with 
pliers or wrench while tighten- 
ing the front nuts with another 
wrench. 

lb complete the assembly of 
the transceiver, place the speak- 
er and grill inside the alumi- 
num housing extrusion and 
fasten It with four No, 6-32 x 
5/16-lnch Philips-head screws, 
Internal tooth lock washers, 
and nuts. Connect all cables to 
their proper jacks on the PC 
board, and slide the assembly 
into the housing. Depress the 
transmit switch SI shaft so that 
it slides into the housing, (The 
transmit switch button cannot 
be attached until the board is 
inserted in the extrusion.) 

Attach the end panels with 
No, 440 self-tapping screws. 
Slide the knobs on the 0,125* 
inch diameter squelch and vol- 
ume potentiometer shafts (R25 
and R26) and lock them in posi- 
tion with a 0,050-inch Allen 
wrench. 

Calibration & troublesliootlng 

Charge the power cells by con- 
necting them to the wall outlet- 



mounted AC to l2-volt DC 
adapter for 24 hours. Be sure 
the power switch is off white 
the power pack is being 
charged. The following test 
equipment is required to cali- 
brate the E-Comm transceiver: 

• OsclQoscope (one that is 50 
MHz or fasterl 

• Frequency counter 

• Digital multimeter 

• Plastic coil- tuning sticks 

• A 50-ohm dummy load 

An FM-modulated RF source 
Is helpful but is not a require- 
ment for calibrating the trans- 
ceiver The 50-ohm dummy can 
be made by wiring ten 470*ohm 
resistors in parallel with short 
leads. Be sure that inductor L8 
is not installed before starting 
the procedure! 

First tune the transmitter. 
Note: whiie adjusting the trans- 
mitter avoid touching any of the 
output circuit components be- 
cause some high voltages arc 
developed there. TUrn on the 
power switch and connect ttie 
oscilloscope leads to pin 1 of 
!C2. the quad'NAND Schmitt 
trigger and observe the wave- 
forms while pressing the trans- 
mit switch, T\veak inductors LI 
and then L2 until a clean sin* 
usoidal waveform is observed, 
(The frequency should be about 
27.145 MHz,) 

Disconnect the oscilloscope 
and attach a frequency counter 
to pin 1 of IC2 through the high 
Impedance input of the counter. 



and adjust inductor L9 to set 
the frequency to 27.145 MHz* 
Reconnect the scope again and 
fine tunc inductors LI and L2 to 
get the best looking waveform. 
The waveform amplitude 
should be between 3 and 6 volts 
peak-to-pcak. if the waveform is 
satisfactorj^. solder Inductor L8 
into the circuit board and at- 
tach the 50-ohm dummy load to 
the BNC antenna jack. 

Attach a current meter in se- 
ries with the power pack or the 
DC supply to adjust the final RF 
ampli^er Hook up the output 
pin of Jl to the oscilloscope and 
set it to 10 volts per division. 
While observing the current 
me ten press the transmit 
switch and look at the wave- 
form. Quickly tweak capacitor 
C30 so that the current is less 
than 400 milliamperes and the 
output voltage across the 
dummy load is about 35 volts 
peak-to-peak- 

To obtain maximum efficien- 
cy^ fine tune inductors LI and 
L2 and capacitor C30 to set the 
output power as close as possi- 
ble to the optimum value. That 
value is expressed as (V^,^^ peak 
X 0,707)2 divided by the in- 
put power (V^„ DC X DC), 
(This is a "trial and error*' step 
that calls for patience,) Do not 
try to set the output to max- 
imum power! 

If the 400-miliiampere max- 
imum input current is exceed- 
continued on page 94 




p probe Is an o^lilgscope ai 
cesson- Uiai permits you*o rake mea- 
k^ufsemenis from two points in a circCMt 
without reference to ground. That eijiables the 
oscilloscope to be safely grounded without tha 
^^.jieed for optoisolalprs or isolation transfor- 
^^^ers. The probe can also make accurate mea* 
'^^urements of small signal differences even in 
tire presence of veo* h*gh common-mode volt- 
age. 

The probe. In effect, moves the input termi- 
nals from the front panel of the scope to the end 
of the probe. The inputs of a dilTerentlal probe 
with appropriate input ratings can. for exam- 
ple, measure power semlcondutor circuits be- 
cause no reference to {ground is needed. Both 
positive and negative sides of the balanced in- 
put offer high Impedance !o ground. High-im- 
pedance difTerential probes increase the Input 
istance and reduce the effective input capac- 
ce of the oscilloscope. 





The low-cost dillerentlal probe shown In Fig. 
1 was designed primarily for induslrfal efcc- ^ 
tronic maintenance applications where AC volt- 
ages up to 500 volts rms are present. TMjIe 1 
gives the leading specifications of that Instru* 
ment. It has selectable attenuation ratios of 
20:1 and 200; 1. ^ 

Figure 3 is a stmpliiied schematic of the dif- 
ferential pmbe showing how it is connecied j 
between the circuit under test and the scope. A ' 
built-in differentf al amplifier converts the htgh- 
voUage difTerential input signal to a low-voli- 
age, single-ended output for a general purpose 
oscilloscope. 

Electronic test labs that perform a wide v^ii- 
ety ni' measurements are likely to own one or 
mort! differential probes. But until recently dlf- 
fen iHial probes have been quite expensive 
(more than 82000). As a result, you might stiU 
see oscilloscopes lluated'' above ground while 
tests of ungrounded circuits are made. White it 
Is neyer recommended, it can be done ^nfdy 
only If low voltages, say I to 28 volts, arc in- 
volved — and profjer safety precautions are 
taken. Some use a battery-ppwered portable 
scope, others remove the ground pin from the 
scope*s AC line plug or find other ways to 
ground" the scope's chassis. 

However, if one is to measure hundreds 
volts in ungrounded circuits, the case of 
oscilloscope and any metal parts touching that 
case are at a lethal potential. The scope operator 
could be electrocuted! That is why demand is 
increasing for low-cost , industrial-strength dif 
ferenttal probes that can make accurate mea- 
surements safely on the factory floor with 
conventional groiuidcd ^ciriural purpose os 
cilloscope. 



1 me 

r thf 

at 
or 

is 

:l 



Learn how to uMe the acUve differential probe to make 
measurements k ungrounded systems — safely 



* Walter Dorfman is a Senior Etectrical 



al Avex Proljes, Inc. 





RG. 1— API MODEL SI-900 ACTIVE DiF- 
FERENTTAL PROBE suitable for making 
measyrements to - 1000 volU DC. 

High-voltage applicatton 

The best way to explain the 
value of a differential probe in 
an industrial setting is to review 
a problem that occurred In an 
ungrounded closed-loop control 
system and that was solved in a 
safe and timely manner with 
the probe, 

A conveyer belt in a manufac- 
turing plant was exhibiting 
radical speed fluctuations: It 
would alternately slow almost to 
a halt and then speed up to a 
rale that endangered nearby 
personnel. Solving this control 
problem was important be- 
cause, unless it was corrected 
promptly the production line 
would be shut douii. 

Figure 3 is the schematic for 
the belt drive in a control system 
closed around a programmable 
logic controller (PLC). The belt- 
drive DC motor is driven by a 
single-phase, full-wave SCR 
bridge that is electrically iso- 
lated from the PLC by four iso- 
lating SCR gate trigger mod- 
ules. The motor is electrically 
isolated from a tachometer that 
sends velocity signals back to 
the PLC, and both bridge and 
motor are electrically isolated 
from the 220-volt AC line by a 
1:1 power isolation transformen 

When the belt was running, 
persons close to it couid ticar 
the sound of the drive motor 
change pitch as they observed 



the erratic belt speed. In at- 
tempting to trace the cause of 
the problem, the first step was 
to connect a conventional dig- 
ital multimeter across the 
motor's armature terminals to 
verify that the belt speed 
changes corresponded with 
motor voltage changes. Then 
the conveyor belt was discon- 
nected from the drive motor 
sheave to verify that the the 
motor*s speed variations were 
not due to variations in belt 
loading, 

lYoublestiOOtmg plan 

A troubleshooting plan was 
formulated to rule out possible 
faults and isolate the cause to 
one or more of the system ele- 
ments. Figure 3 shows that the 
PLC is referenced lo Earth 
ground. But the rest of the cir- 
cuit is isolated from ground to 
prevent a build-up of damaging 
or hazardous potentials, due to 
an insulation failure, within the 
motor-driven conveyorbelt sys- 
tem. An oscilloscope referenced 
and connected to Earth ground 
cannot make accurate measure- 
ments in a circuit that is not 
referenced to the same ground- 

The maximum peak-to-peak 
voltage that could appear in the 
bridge is about 622 volts, based 
on the characteristics of a sine 
wave for 220-volt AC, (The rms 
voltage must be multiplied by a 



TO THE 
CIRCUIT, 

mom ^ 

TEST 



BLACK 



AHENUATIOH 
NETWOBK 



factor of 2.83 to obtain the 
peak-to-peak voltage,) Exam- 
ination of the control diagram 
showed that differential mea- 
suremcnt techniques were 
needed to make accurate and 
safe measurements of this 
"floating" system. 

It would be necessary lo check 
logic-level SCR gate signals 
riding on the 220-volt AC line. 
Any differential probe suitable 
for making those measure- 
ments had to be capable of can- 
celling the large pcak-to-peak 
AC waveform, leaving only the 
desired logic-level signals, esti- 
mated at 3 and 12 volts DC. for 
analysis. 

The differential probe was 
first connected to Earth ground 
with the oscilloscope (BNC) con- 
nector. Then the probe was con- 
nected to the oscilloscope. In 
this case, the internal power 
supply was used so the probe 
coitld then be turned "on. 

Knowing that voltages in ex- 
cess of 622 volts AC peak-to- 
peak would be present, a probe 
attenuation range of 200:1 was 
selected. (Table 1 shows that for 
the probe used, the maximum 
working voltage to ground and 
between inputs is 500 volts 
rms. and the maximum non-de- 
structive input Is 700 volts AC 
rms or 1000 volts DC.) 

The 622 volts is divided by 
200 to become a 3Jl-voit sig- 





DC TO DC 
CONVERTER 












TO 

OSCILLOSCOPE 



DIFFERENTIAL 
-V AMPLIFrER 



1 



RG. 2— A SCHEMATIC OF AN ACTiVE DIFFERENTIAL PROBE that can be internalty 
powemd by four IS- volt celts or an AC to OC converter 



TABLE 1- 

Bandwidth 
Accuracy 
Attenuation ratio 
Input resistance 
Input capacitance 
Input range 



Max, common 
mode input 

Common mode 
rejection ratio 

Max. output 

Output offset 

Power requiJBmenls 



-LEADING SPECS OF API PROBE 
DC to 15 MHz 
±2% (nominal) 
20:1 and 200:1 (selectable) 
2 Megohms 

26 pF (each side grounded) 

± 700 V 00 f peak AC 
(200:1 attenuation) 

-70 V DC peak AC 
(200:1 or 20:1 attentualion) 

600 V rms 

70 dB (it 1 kHz 

±3.5 V into 1 Megohm 

±5mV (10'C to 40=^ C) 

Four 1.5 VAAceJls or 
6 V DC. 50 m A adapter 



I 



PROGRAMMABLE 
LOGIC 
CONTROLLER 



ISOLATING 
SCR GATE 
TRIGGER MCDULfS 



220V 
AC 



SCRl 



SCR2 



iSOLAHON 
T1WSFDRMEH 

r 1 



I 



5CR3( 



SCR4 



ISOLATED 
TACHOMBER 



RG, a— A CONVEYOR BELT SPEED CONTROL system, isolated from Earth ground. 
Indudes a programmable togtc controller (PLC), a futUwave, smgle^phaseSCR bridge. 
DC motor with isolated tachometer, and four isolating SCR gate^ triggering modules. 



nal. ITtie displayed output volt- 
age had to be kept within the 
±3,5 volts limit of the probe J 

The two probe input le^ids 
were then carefully connected 
across the 220-volt AC line feed- 
ing the 1:1 isolation trans- 
formen The oscilloscope dis- 
played the 3.11-volts peak'to- 
peak sine wave shown in Fif(. 4- 
a. The regularity of the scaled - 
down sine wave showed that 
there were no faults in the line 
voltage. 

Both probes were moved to 
the secondar\^ of the isolation 



transformer and a waveform es- 
sentlally the same as the 622- 
voll peak-to-peak sine wave- 
form of Fig. 4*a appeared; it is 
shown as Fig* 4-b. However, 
small distortions and ampli- 
tude changes were seen on the 
negative peaks* and they were 
in s^Tich with motor-speed vari* 
at ions. The electrical noise in 
the waveform was believed to be 
due to the reflected loading 
effects of the motor's power and 
speed changes. 

The differential probe leads 
were than connected across the 



motors armature, and the 
periodic high-frequency oscilla- 
tions shown in Fig. 4-c were 
seen. Their occu ranee matched 
the motors speed variations* 
Next the probe was connected 
across the anode ( + ) and cath- 
ode ( - ) terminals of each of the 
four SCR's in the bridge, and 
their waveforms were observed. 

As shown in Fig. 5, all the 
SCR s exhibi ted some waveform 
distortion, butoneof them» Fig. 
5-c exhibited more severe dis- 
tortion than the others. 

As the next step, the probe 
was connected across the gate 
( + } to cathode { - ) terminals of 
each of the three SCR's that 
showed lower anode-to-cathode 
noise voltages. The differentia! 
probe successfully cancelled the 
622 volts peak'to-peak AC on 
which the gate-to-cathode volt- 
ages were riding. The result was 
clean, normal gate trigger wave- 
forms with nominal 3 -volt 
peaks, as showm in Figs. 6-a, 6- 
b, and 6-d. 

However, the remaining 
SCRs gate*to-cathode voltage 
waveform. Fig, 6-e, showed 
time-varying gate-trigger 
pulses. (Il was the same SCR 
that had shown the highest 
anode-to-cathode jitter in Fig, 
5-c,] Some pulses in Fig. 6-c 
started earlier and others slart- 




flG. 4— VOLTAGE WAVEFORMS viewed 
at 220-voll AC input; transformer pri- 
mary a, transformer secondary d, and 
motor armature {joad) c. 




(f 



FIG. 5— ANODE-TO CATHODE VOLT- 
AGES viewed at each bridge SCR (trig- 
gered at 90 into a positive p€ak supply 
voitage): SCR1 a, SCR2 SCR3 c, and 
5CR4 

ed later than the nominal times 
seen for the other three gate-to- 
cathode waveforms* 

Identifying the culprit 

A pattern had now been es- 
tablished linking the trouble to 
one SCR channeL It was next 
decided to determine the quali- 
ty of the output signals from tlic 
PLC, lb observe the PLC output 
lines* which are referenced to 
system/Earth ground, the black 
( - ) lead of the difTerential probe 
was connected to system 
ground. Because 1 2 -volt logic 



signals were to be viewed, the 
differential probes attenuator 
was switched to 20:1 {12 volts/ 
20 = 0.6 volt), and the o^s- 
cilloscope's vertical sensitivity 
ofO* I volt/division was selected. 
Three of the four 12- volt logic 
signals from the PLC to the SCR 
gate-trigger lines appeared nor- 
mal* as shown in Fig, 6-e* 64, 
and 6-h. However, the Fig. 6-g 
waveform was distorted by low- 
level reflected noise that tracked 
with the motors speed varia- 
tions. It was the same SCR 
channel that had shown gate- 
to-cathode electrical noise in 
Fig- 

That finding narrowed the 
cause of the problem down to 
one SCR channel and it was 
thought to be either a faulty 
PLC-to-SCR gate isolating trig- 
ger module or a malfunctioning 
SCR* A new plug-in module was 
then substituted for the one 
that appeared to be faulty and 
the problem was quickly solved. 

The differential probe dis- 
cussed in this article is sold in 
the United States by three dif* 
ferent suppliers: Avex Probes 
Inc, (API) as the Sl-9000: Test 
Probes. Inc*{TPl) as the ADF15, 



* 

3V 1 




1 




i 


3V 


1 






T 

3V 


1 


11 . 


3V 








d 


T" 

+ 12V 




















0 

412V 










0 








t 


412V 


REaECTEO 


0 — 
4l2V 










ft 








ft 





RG, 6— GATE-TaCATHODE VOLTAGES 
viewed at the Input of gate terminais of 
SCRI to SCR4 a, b, c, and and output 
signals from the PiX a, b^ c, and d. 



PROBE SUPPLIERS 

Avex Probes Inc. (API) 
PO Box 1026 
Bensalem. PA 19020 
215-638-3300 

CIRCLE 316 ON FREE INrOFIMATlON CARD 

Hewlett-Packard 

PO Box 612350 

San Jose, CA 95161-2350 

800-452'4848 

CIRCLE 317 ON FREE INFORMATION CARD 

ITT Pomona 

1500 East Ninth St. 
Pomona, CA 91769 
714^9-2900 

CIRCLE 318 ON FREE INFORMATION CARD 

Jensen Tools, Inc. 
7815 South 46lh St. 
Phoenix, AZ 85044^5399 
602-968-6231 

CIRCLE 319 ON FREE INFORMATION CARD 

Probe Master Inc, 
4898 Ronson Court 
San Diego, C A 92111 
800-772-1519 

CIRCLE 320 ON FREE INFORMATION CARD 

Tektronix 

PO Box 50 
Beaverton, OR 97077 
503-627-7111 

CIRCLE 321 ON FREE INFORMATION CARD 

Test Probes, Inc, (TPI) 
9178 Brown Deer Road 
San Diego. CA 92121 
(616} 552-2090 

CIRCLE 322 ON FREE INFORMATION CARD 



and Probe Master as the 
PM4230. 

For purposes of comparison, 
consider two other differential 
probes, the Tektronix P6046 
and the Hewlett-Packard HP 
U41A/1142A. The Tektronix 
system consists of three sepa- 
rate cable- connected units: a 
probe head, an amplifier and an 
AC4ine operated power supply. 
It has a common-mode reject ion 
ratio (CMRR) of 10.000:1, an in- 
put resistance of I megohm, 
and an input capacitance of 10 
p Ic o farads , I ts m ax 1 m u m ba nd- 
width is 100 MHz, and its max- 
imum DC plus peak AC is ± 250 
volts. 

The HP 1141A differential 
probe is a 1 X FET differential 
probe with a 200-MHz band- 
width and a CMF'tR of 3000:1, 
The probe has an input resis- 
tance of 1 megohm and an input 
capacitance of 7 picofarads. It 
must be used with the HP 1142A 
probe control and power mod- 
ule system, R*£ 



FROM 

NotWorkiimg 
^NETWORKING 

Bring your knowledge to bear 
on several tough LAN case histories. 



PARTS 1 AND 2 OF THIS THREE-PART 

series on troubleshooting LAN s 
presented technical back- 
ground on network tech- 
nologies (in Part IJ, and on tools 
and test equipment (in Part 21 
This time we put our knowledge 
to work in diagnosing and solv- 
ing network problems of vary- 
Ing difficulty. 

In each case, we will describe 
the type of LAN, symptoms 
manifested, fault isolation tech- 
niques, use of test equipment* 
and repair methods, lb follow 
the discussion* It is important 
to have at least a basic under* 
standing of LAN technologies 
and test equipment as de- 
scribed in parts 1 and 2, So if 
you are unsure about anything 
discussed so far, reread those 
parts before continuing. 

The computer ate my work! 

This one happened at a local 
metal fabrication shop: the 
symptoms drove the company s 
finance people up the wall! That 
shop had five XT clones commu- 
n teat ing with an IBM PC- AT file 
server via Ethernet, For a long 
time, the network had been re- 
liable, but after several years of 
use. it began to run slower and 
slower whenever users ran 
order entry and accounting pro- 
grams off the file server. Error 
messages began to appear, and 
sometimes users had to repeat 
the process, TVouble shoo ting 
began when several people in 
the order entry department 



GARY McCLELLAN 

complained of trashed data. 

Several users were affected, 
so it seemed unlikely that their 
computers were at fault. That 
left the Ethernet backbone ca- 
ble and the file server as sus- 
pects. The backbone cable 
could have been the problem, 
but it didn't seem likely Then 
someone discovered that a sel- 
dom-used word-processing pro- 
gram ran fine, so we ruled out 
the possibility of cable fault. 
That left the file server and hard 
disk £is a possible culprit. 

That evening we shut down 
the network and ran a "disk 
doctor" program on the file serv- 
er. Those programs are available 
from several sources, including 
Symantec (Norton Utilities), 
Central Point Software (PC 
Tools), and Gibson Research 
(SpinRlte), What these pro- 
grams do is perform a non*de- 
structive low-level format of a 
disk drive. Typically such pro- 
grams work by reading a track 
of data from the drive, format- 
ting that track, and rewriting 
the data. Any bad sectors de- 
tected along the way get mapped 
out. and the data gets moved 
elsewhere, if possible. Figure 1 
shows a sample screen from the 
Calibrate utility included with 
versions 6.x of the Norton Utll- 
Itfes. 

A related function often goes 
by the name o{ disk defragment- 
ing, which attempts to group 
logically related segments of a 
file together physically in con- 




secutive sectors of a disk. Doing 
so can dramatically increase the 
speed with which DOS reads 
files. A disk becomes frag- 
mented because, when a file is 
erased, DOS subsequently adds 
the now-unused sectors to a 
pool of sectors that might sub- 
sequently be reused. A par- 
ticular group of erased sectors 
might not contain enough 
space to hold an entire file, so 
DOS puts parts of the file In 
non-adjacent areas across the 
disk. The result is that when 
loading the program or data file, 
DOS sends the" read/write head 
all over the surface of the disk, 
rather than lapping up sectors 
one by one. That jerky head mo- 
tion can really slow things 
down. It is not unusual for over- 
all operation to be speeded up by 
10-20% or even more simply by 
"doctoring * the hard disk, Nor- 
ton and Central Point both in- 
clude disk defraggers as well, 

Anw'ay running a disk doc- 
tor program on the fabrication 
shops server solved the prob- 
lem. Tb avoid that type of prob- 
lem, run a disk doctor program 
a minimum of every sbc months 
to catch bad cylinders and pre- 
vent data loss. If you encounter 
many bad cylinders, say 5% or 
more, you should replace that 
hard disk before a catastrophic 
failure occurs! 

The dead PC 

Many LAN problems go like 
this: A user cannot log onto the 




network, or a PC suddenly 
drops offline — but other users 
remain unaffected. Following 
are two examples of this type of 
problem, along with corre- 
sponding solutions. 

Example one occurred In a 
parts distributors office. The 
LAN consisted of five clone PC's 
and a generic 80286 file server 
tied together via ARCnct. 
ARCnet operates over RG-58 
thin coaxial cable that runs 
from computer to computer 

First, we tested the sick PC 
off-line and found it to be func- 
tional. That left the Network In- 
terface Card (NIC) and LAN 
cabling as suspects. First we In- 
spected the coax cables and they 
looked good. But a gentle tug on 
a loose BNC cable connector 
caused it to come off. Replacing 
the connector brought the com- 
puter back to life. 

Generally speaking, con* 
nector faults are a major prob- 
lem on LANs. Most BNC 
connectors are cr Imp-on types, 
and if installed improperly, 
eventually they fall — but not be- 
fore becoming intermittent and 
causing lots of grief! Connector 
problems usually develop sev- 
eral years after their initial In- 
stallation; often they're caused 
by oxidation of contacts. For 
problem Installations, we prefer 
soldered to crimp-on BNC con- 



nectors. They take 5 to 10 min* 
utes longer to Install, but are far 
more reliable. 

Many connector problems are 
caused by users who acciden- 
tally damage cables by crushing 
them under chair legs, or drop- 
ping equipment on them. Our 
troubleshooting kit includes a 
collection of 10-foot cables 
which have coaxial BNC con- 
nectors, triple twisted-pair 
RJ-11 connectors, and quad 
twisted-pair RJ-45 connectors. 
The cables are for on-site sub- 
stitution of questionable ca- 
bles. 

Example two In this category 
concerned a dead computer in a 
medical billing office. The com- 
pany used five IBM PC*s linked 
by telephone-type unshielded 
twisted pair {UTP3 cabling into a 
Compaq 386 configured as a 
hub. The hub serves as both a 
file server and as a central point 
to which all cabling returns. 

We tested the problem PC, 
and it appeared to be working. U 
just wouldn't log onto the net- 
work. We substituted a different 
drop cable between computer 
and wall outlet: the new cable 
worked for a while and then 
quit. Next we substituted a PC 
from the office of a vacationing 
user* but without success. 

At that point the problem 
could have been anywhere, in- 



cluding the computer, its NIC, 
the cable plugged into the wall 
ouUet, or even the wiring back 
to the hub. 

First* we checked the old waU 
cable with the Paladin 
PatchCheck tester (discussed in 
the last article), PatchCheck 
checks cables in seconds, if you 
can access the modular plugs 
on both ends. Pin 2 showed a 
dim indication on the tester, 
suggesting high resistance. We 
didn't know which end was bad. 
so we replaced the connectors at 
both ends. The cable then test- 
ed good, so we reinstalled it and 
were able to log onto the net- 
work briefly But then trouble 
developed again. On a hunch, 
we pushed and held the modu- 
lar connector in the waU outlet. 
The user could log onto the net- 
work and work normally — until 
we let go of the connector. Then 
the PC crashed. Replacing the 
wall outlet solved the problem. 

In general, most twisted-pair 
cable problems are caused by 
bad crimps or by users pulling 
individual strands out of the 
connectors. In the present case, 
the initial installer used cheap 
connectors that probably were 
not crimped fully which in turn 
caused resistance to increase 
over time. As for the wall outlet, 
close inspection showed that 
the pins were partly covered by a 
greenish film, probably caused 
by moisture in the wafi corrod- 
ing the faulty gold plating on the 
pins. 

If you want to avoid a career in 
connector replacement you 
should always use qustlity cable 
and wall-socket connectors. 

Warehouse madBess 

The problems described so far 
represent roughly 80% of the 
faults you will encounter on 
computer LAN's, But there are 
other kinds of problems that 
will tax your troubleshooting 
abilities, and that also require 
specialized test equipment. Our 
next case is a good example. 

A firm relocated to a new 
headquarters 100 miles away 
leaving behind a warehouse. 
The new system used an IBM 
mldrange computer (at head- 
quarters) and CRT terminals 
and printers {in the ware- 



house), all connected via mod- 
ems and a dedicated telephone 
line. The purpose of this ar- 
rangement was to generate cus- 
tomer shipping orders. One day 
all the terminals and printers In 
the warehouse stopped cold. 
The data processing manager 
(DPM) of the company found 
that his equipment was not 
working properly, and he 
blamed the tetephone line. The 
local telephone company check- 
ed its line and pronounced it 
good! So where was the prob- 
lem? 

One possibility was that the 
fault was somewhere in the 
warehouse, between the 
modem and the outside line 
connections. With permission, 
we inspected the modem wiring 
in the telephone cable closet. It 
looked good* but then we mea- 
sured the line voltage with a 
DMM, It read zero! We had ex- 
pected 2 to 10 millivolts of AC 
noise, typical on a terminated 
line, A quick resistance check 
showed 7 ohms. There was a 
short in the wiring! 

We then spent several hours 
walking between modem and 
cable closet* disconnecting wir- 
ing, and eliminating various 
suspects. One look at the huge 
bundles of wiring on the wall of 
the building was enough to dis- 
courage fault finding by visual 
inspection! 

The solution was to use a time 
domain reflectometer (TDR), 
which can locate faults along 
the cable. After making sure the 
outside telephone line and 
modem cable were still discon- 
nected, we attached a MlcroTest 
Cable Scanner handheld TDR 
to the line in the closet. The 
TDR indicated some irreg- 
ularity about 70 feet away, 
which put the fault near the 
modem. Then we made another 
measurement near the modem 
end, and the cable scanner indi- 
cated a dead short. 

Then we traced the wiring 
into a storage closet where the 
red and white twisted-pair cable 
ran through a hole in a steel 
riser and up the wall. Close in- 
spection of the wires running 
through tlie hole revealed that a 
sharp edge had cut through the 
insulation and shorted the ca- 



ble. Insulating the wires with 
electrical tape brought the net- 
work back on-line. 
The problem of different or- 



NETWORK BACKGROUND 

The following am reference materi- 
als, equipment suppNers. and network- 
related standards organizatkins. 
References: 

• The Practical Guide to Local Ama 
Networks, Rowland Archer Osix)rne* 
McGraw Hill. Good inlroduction to cable 
types, topologies, artd access methods* 

• Neiworkir}g IBM PC's, Michael Durr, 
Que Cofpofalion. Chapter 14 contains 
good ovenflew of bridges, routers, and 
gateways. 

« LAN Magazine, 600 Hanison Street, 
San Francisco. CA 94107 (415) 
905-2200. 
Suppfiers: 

• Black Box Corporation, P,0, Box 
12800, Pittsburgh. PA 15241, {412) 
746-5530, 

• Cable Express Corporation^ 500 East 
Brighton Avenue. Syracuse, MY 13210, 
(ai5) 476-31O0, 

• Coniaci East. 335 Wilto Streei South, 
North Andover. MD 01845. (508) 
688*7829 

• JDR Microdevices. 2233 Samaritan 
Drive, San Jose. CA 95124. (800) 
538-50OO. 

• Jensen Tools. Inc., 7815 S. 46th 
Street. Phoenix. AZ 85044. (602) 
968^6231. 

Standards Organizations: 

• American National Standards In* 
stitute. 1430 Broadway, New York, NY 
10018. (212), 642-4900. 

• IEEE Headquariers. 345 E. 47m 
Street, New York, NY 10017-2394, (212) 
705-7900. 



RESOURCES 

The following are addresses of man- 
ufacturers whose products were dis- 
cussed in this series of articles. Contact 
those companies for current pricing and 
more information. 

• F^adin Corporation, 3543 Old Corre- 
p Rd.. Newtjury Park. CA 92123. (800) 
272-8665. 

• MiCfoTest, lnc.» 3519 E. Shea Blvd. 
Suite 134, Phoenix, AZ 85028, (800) 
526-9675. 

• Radio Amateur's Han(iboof<, 
American Radio Relay League, New- 
tngton. CT 06111. 

• Tektronix, Inc., Redmond Division, 
625 S. E. Salmon Dr, Redmond. OR 
97756, (800) 833-9200. 

• AA^PJnc., RO. Box 3608, Harnsburg, 
PA 17105, (717) 561*6168. 

• Gibson Research. 22991 La Cadena 
Dr.. Laguna Hills, CA 926S3. (714) 
830-2200 

• Symantec Corp., Norton Utilities. 
10201 Torre Ave.. Cupertino. CA 
95014-2132. {408) 253-9600. 



ganizations blaming each other 
for faults neither can trace is 
common, because most LANs 
consist of different products 
from different vendors, includ- 
ing computersi terminals, 
printers, modems, NIC*s. ca- 
bles, and more. The solution is 
to leam about your LAN equip- 
ment and service it yourself, or 
find a trustworthy service firm 
that can do it for you. 

Cloak and dagger 

We saved the most fascinating 
LAN servicing case for last. After 
this case was resolved, someone 
must have answered some in- 
teresting questions about his 
late-night activities. 

Here's what happened: A soft- 
ware development firm became 
highly distressed when several 
of Its workstations performed 
intermittently in the middle of a 
rush project. The firm promptly 
called Its regular service compa- 
ny, which In turn concluded 
that there was a bad cable con- 
necting those machines and the 
rest of the LAN. The service 
company recommended tearing 
the old cable out of the wall and 
replacing it. After considering 
the cost of a new cable Inslalla- 
tlon. the firm asked that it be 
repaired instead. 

At this point we were called in 
to provide a second opinion. 
Wisely, the service company had 
bypassed the bad cable with a 
temporary one; thus wc could 
test the bad cable without shut- 
ting down the LAN, This net- 
work used a series of high-end 
workstations tied together via 
an ARCnet system into a mini- 
computer. A 60- to 100-foot 
length of coaxial cable con- 
nected the LAN with the last two 
workstations in the chain » We 
knew that the cable between 
them and the LAN was at fault. ^ 

We started troubleshooting by B 
making continuity checks on ? 
the wiring. Instead of an open 3 
circuit, our DMM showed 10 r§ 
ohms between the shell and 01 
center conductor of one of the | 
BNC connectors extending from 1 | 
the wall. a ' 

There was definitely a short in g li 
the cable. But where was it lo- ^ 
cated? Our initial response was 
to confirm the service compa- 67 



OFF 



AC 1 : 1 i ! i 


i 159.2m ; 




: * I 






: : : 




1 : ^ ill * : * ; 






fTin i ll :U . 1 ui 
: " : II r : i : 


✓ • ; I 
I * * 






* ' I 




: : : : 1 : 


* * * 




i 1 ; 1 ! i 

* * " 1 . ' 

' - ■ r * 

* ■ * ; ■ 

* » * ' 1 


■ • » 
: i : 



m 

OFF 
OFF 
OFF 




AC ; i : 


] : ; 29.52mA : 


: : : : t : : 




* * I * 
1 : : = ' 


i : I 
% I I 








r * • • * 

I ■ 4 « m 








r 




1 : 
1 ; 1 






r : ; 




I * * % Y w * 

: : : : 1 : : 

-•^ , ^_ 





FIG* 2— A GOOD ETHERNET CABLE appears like this on a time domain reflectomoter 
(TDF^)» which shows fmpedance vs. dbtance. The vertical line In a marks the end of the 
cable. In the vertical line represents a bad cable tap. The TOR can "zoom" into the 
display, and c shows an expanded view of the bad tap. 



z 

n 



nys assessment, and to recom- 
mend tearing out the old cable. 
However, we first decided to do 
some troubleshooting. 

We rented a Tfektronlx model 
1502C analog TDR from a local 
instrument rental company, 
(Rental is recommended any- 
time you need an expensive 
piece of equipment for just a few 



days,) We chose this premiere 
TDR because it displays minor 
faults that digital TDR's often 
miss. In the past we have lo- 
cated rusty connectors, loose 
connectors, and watersoaked 
cable sections with the 1502C. 
all of which w^re missed by a 
digital TDR. The dovm side of 
an analog TDR is that it re- 



quires more skill to use. 

The 1502C displays distance 
vs, impedance on an LCD 
screen. The display shows, 
along the entire length of the 
cable, a continuous "snapshot" 
of Impedance, which in our case 
was supposed to be about 50 
ohms. Shorts cause the trace to 
drop to 0 ohms, and opens 
cause the trace to rise off the 
display. In operation, you look 
for suspect drops and rises, 
read the distance directly off the 
display, and start troubleshoot- 
ing at the specified location. 
Figure 2 shows several exam- 
ples of TDR displays. 

After connecting the TDR to 
the cable, we checked the dis- 
play» which showed the ex- 
pected 50-ohms. but with a 
sharp drop about 29 feet away A 
company manager, who had 
been looking over our 
shoulders, suggested that we 
check the celling* We lifted cell- 
ing panels and located the ca- 
ble. Since we had no idea of 
distance in the ceiling space* we 
guessed at the location and In- 
spected cable for some distance 
each way from our access point. 
Above a service closet we found 
the culprit. Someone had sliced 
the cable open and crudely 
spliced another cable to it. 

Upon closer inspection, we 
noticed that the added cable 
was pulled taut, causing 
strands from the uninsulated 
connections to touch. That, in 
turn, reduced signal levels to 
the workstations, causing Inter- 
mittent problems. With excite- 
ment» we traced the second 
cable into a closet where we 
found a computer and a printer 
hidden behind a row of shelves. 

We showed our findings to the 
manager. He said he would 
watch the closet and determine 
the identity of the eavesd ropper 
A week later he called the service 
company and had them remove 
the splice and replace it with a 
crlmp-on BNC connector and a 
barrel adapter. Later we heard 
that the computer had been re- 
moved from the closet » but the 
manager would not say whether 
he had caught the guilty per- 
son. If it hadn^t been for the 
short, we might never have dis- 
covered that illegal tap! H-E 



THIS ARTICLE LOOKS AT THE VER- 

satile 555 monolithic integrated 
timing circuit as an asiable 
multivibraton the illp-sidcorits 
capabilities as a inonostable 
multivibrator in time-delay cir- 
cuits, A recent article (Sep- 
tember R-E. pg, 58) explored tlie 
role of the 555 in the monosta- 
bie mode. 

Now youli find out how to 
build many different kinds of 
circuits with the 555 contigurcd 
as a self-triggerlng oscillaton 
You will want to build the cir- 
cuits that can generate a variety 
of square or rectangular wave- 
forms, wail like a police car. imi- 
tate the jarring he- haw sound of 
European emergency vehicles^ 
or reproduce the i^laxon alarm 
of the Star Treks' starship Enter- 
prise. 

The last article on the 555 as a 
monos table multivibrator in- 
cluded a functional block di- 
agram and an electrical sche- 
matic of the chip. You might 
want to refer back to those fig- 
ures if you want more detailed 
information about how the 555 
is organized. Figure 1 is a pin- 
out diagram of the 555 as pack- 
aged in the most common 8-pin 
DIR It was pointed out in the 
last article that, although a ma- 
ture device, the 555 remains 
one of the most popular IC's 
available today 

At least five major semicon- 
ductor firms in the U.S, and Ja- 
pan make the 555, There is also 
a dual version, the 556, that has 
two identical 555 *s on a single 
chip. The device is usually pack- 
aged in a 14-pin DIR A quad ver- 
sion, the 558, has four inden- 
tical 555 's on a single chip, and 
it Is packaged in a 16-pin D!R 
The alternate source stippiiers 
usually include the numerals 
55, 56 or 58 in their own desig- 
nations for those devices. 

The 555 occupies a strange 
position in the universe of inte- 
grated circuits. Classed as a lin- 
ear IC because it can be 
triggered either by linear or dig- 
ital signals, its output is always 
digital — in the form of rec* 
tangular or square waves or 
pulses. 

The 555 in a monostabie mul- 
tivibrator circuit (also called a 
timer, time delay, or one-shot) 



THE 555: 

A VERSATILE 

OSCILLATOR 



Learn how to build the 555 IC into 
osciilator circuits whose frequency you can 
change so they^li wail, warble^ and honk. 

RAY M. MARSTON 



generates a fixed-length output 
pulse for each trigger pulse at 
its input. This can be demon- 
strated with the circuit in Fig, 
2. By contrast, the 555 in an 
astabie multivibrator circuit is 
shown in Fig. 3. It has no stable 
output states and no external 



1_ 








GROUND 






2 


TRIGGER 


m 


OlSCKARGf 


3 


oirrpuT 


THRESHOLD 


4 


RESET 




CONTROL! 
VOLTAGE 



Astabie operation 

In the monostabie multi- 
vibrator circuit in Fig. 2, OUTPUT 
pin 3, DISCHARGE plu 7. and 
THRESHOLD pin 6 are held low 
when the circuit is quiescent. A 
monostabie timing period can 
be started by driving trigger 
pin 2 low with pushbutton 
switch Si, That causes output 
pin 3 to switch high, while 
DISCI u\RGE pin 7 is released and 
free to follow the voltage across 
CI. Voltage rises exponentially 
through Rl toward the supply 



FIG. 1— PrNOUT DIAGRAM OF THE 555, 

trigger is necessary to start cir- 
cuit oscillation; it is said to be 
self-triggering. This circuit con- 
figuration is also called an 
osciHator, signal generator 
pulse generator, or a rectangle- 
wave generator. 

As long as power is applied to 
the astabie circuit, the output 
continually switches back and 
forth between the high and low 
states at a regular rate or fre- 
quency The time in the high 
state (pulse width) and the time 
in the low slate (space length) 
depend on the selection of exter- 
nal resistors and capacitors. Be- 
cause of its relatively high 
output, the 555 in an astabie 
circuit can drive LED's. speak- 
ers, and meters directly. 



+ 5VT0 + T5V 



-m 



Rl 
22K 



8 4 



555 



33#iF 



22K 



HS1 
START 



I- - \,< OUTPUT 
i 1 i 



FfG. 2 — MONOSTABIE MULTh 
VIBRATOR TIMING CIRCUIT based on 
the 555. ^ 

v^okai^e. Eventually the voltage 
at pin 7 rises to t\^'o- thirds of 
the supply voltage, and mono- 
stable action ceases with pins 3, 



% 

IP 
m 



2! 



69 



6 and 7 grounded by the inter- 
nal circuitry of the 555. 

Examine the astable circuit 
shown in Fig, 3-a, in this circuit 
TRIGGER pin 2 is shorted to 
TMKKsiiOLD pin 6, aiid timing re- 
sistor R2 is wired between pin 2 
and DISCHARGE pin 7. When 
power Is applied to the circuit, 
capacitor CI charges exponen- 
tially (as it did in Fig, 1) through 
resistors Rl and R2 until the 
voltage on CI reaches two- 



+5VT0 + 15V 



Rl 
IK 



^: R2 



a 4 



5S5 



I 




1 



oumrr 



OUTPUT 

M m 3 

OUTPUT 
ACROSS 
€1 



FIG, 3— A ONE-KILOHERTZ ASTABLE 
MULTIVIBRATOR based on the 555, 
and waveforms at output pin 3 and 
across CI are shewn la d. 

thirds of the supply voltage. At 
that time, monostable action 
ceases and discioirge ptn 7 re- 
turns to its low state. Capacitor 
CI then discharges exponen- 
tially into pin 7 through R2 un- 
til the voltage on CI falls to one- 
third of the supply voltage, and 
TRIGGER pin 2 Is activated. 

At that time, a new monosta- 
ble timing sequence is started 
and CI recharges to two- thirds 
of the supply voltage through re- 
sistors Rl and R2. The whole 
sequence then repeats itself 
over and over with CI alter- 
nately charging to two-thirds of 
the supply voltage through Rl 
and R2, and then discharging 



to one-third of that voltage 
through R2 only 

Notice that in Fig, 3-a, the val- 
ue of R2 Is very large with re- 
spect to tlie value of RL It turns 
out that the oscillation frequen- 
cy of the circuit is largely deter- 
mined by the values of R2 and 
C2. Figure 3-b shows the nearly 
symmetrical square output 
waveform that appears between 
OUTPUT pin 3 and ground while a 
nearly linear triangle waveform 
is simultaneously generated 
across CI. 

The grapii of Fig. 4 shows the 
relationship between the free- 
running frequency of the cir- 
cuit in Fig. 3-a and the capaci- 
tance values of CI w\ih the 
range of R2 values shown on the 
diagonal lines. In this graph the 
contribution of resistor Rl is 
neglected because it is a frac- 
tion of the R2 value. 

























































\ 




\ 



1 to m IK 10K 
F. Fn^-CU/NlltNG RHWCV (Hi} 



lOQK 



FIG. 4-THE FREE-RUNNING FRE- 
QUENCY OF OSCILLATOR In Fig. 3 as a 
function of capacitance values for C1 
and tfie resistance value of R2 (when 
large with respect to Rl)* 




FIG, 5— THIS SQUARE-WAVE GENER- 
ATOR produces a variable frequency of 
650 Hz to 7.2 kHz, 




FIG. 6— AN STABLE MULTIVJBRATOR 
with independent pulse width and space 
penods variable from 7 to 7S0 mlcrose* 
conds. 




FIG. 7— ALTERNATE VERSION OF OS- 
CILLATOR shown in Fig. 6. 

The values of Rl and R2 can 
be varied from 1 kilohm up to 
tens of megohins. Resistor Rl 
can, however, have a significant 
effect on the total circuit cur- 
rent consumption because pin 
7 is essentially grounded during 
half or the oscillation cycle. The 
duty cycle or pulse width-to- 
space ratio of the circuit can be 
preset at a nonsymmetrical val- 
ue Jf desired, by the choice of Rl 
and R2 values. 

The high time (pulse width) 
and low lime (space length) in 
this circuit must be calculated 
separately The pulse width cal- 
culation includes the values for 
the timing capacitor CI and 
both timing resistors Rl and 
R2, By contrast, the space 
length formula includes only 
the values of timing capacitor 
CI and resistor R2. 



Refer to Fig. 3-b. Pulse width 
(or time to charge capacitor CI 
is: 

tt - 0,7 CI (Rl +i^2] 

Space iength or time io dis- 

cliarge capacitor CI is: 

t.^ = 0.7C1R2 

The total cycle time is: 

T - t, +tj 

The ratio of pulse undth to the 
total cycle time Is the duty cycle. 
In a 555-based oscillalon tlie 
duty cycle is defined by the rela- 
tive values of the two timing re- 
sistors Rl and R2: 
Duty cycle = R2/[R1 -!-2R2) 
Frequency in hertz (Hz) is the 
reciprocal of total cycle time: 
F = l/T, 

Tiie circuit in Fig. 3-a can be 
modified in many different 
ways. Figure 5, for example, 
shows how it can be made into a 
variable- frequency square- wave 
generator by replacing R2 with 
a fixed resistor and polentiome- 
ter in series. The frequency can 
be varied over a range of about 
650 Hz to 7.2 kHz with the val- 
ues of the resistor and potenti- 
ometer R3 showTi. If required, 
the frequency span can be fur- 
ther increased by switch-select- 
ing alternative values of 01. 



R3 
IDOK 



Dt 
1N414A 

1fM14S* 



.Of 



IK 

-w — r 



fK 



555 



.01 



OUTPUT 



i 



RG. 8— A 1,2 kHz OSCILLATOR with a 
duty cycle vadatite trom 1 to 99%. 



Widiii-space control 

The circuit in Fig. 3-a can 
generate a fixed-frequency out- 
put waveform with any desired 
pulse widlh-to-space iength 
ratio by selecting tlie appropri- 
ate lvalues for Rl and R2. In each 
operating cycle, CI aitemately 
charges through Rl and R2, 



and discharges only through 
R2. For example, if Rl and R2 
have equal values, the circuit 
will generate a 2:1 width-to- 
space ratio. 

The widih-to-space periods 
can be independently con trolied 
with either the Figs. 6 or 7. in 
Fig. 6, CI alternately charges 
through RL diode DL and po- 
tentiometer R3. and tt dis- 
charges through potentiometer 
R4, diode D2, and R2. In FSg. 7, 
CI aitemately charges through 
Rl, potentiometer R3, and di- 
ode Dl, and it discharges 
through potentiometer R4, di- 
ode D2. and R2. In both Fig, 6 
and 7 circuits, R2 protects tlie 
555 if potentiometer R4 is 
shorted. 



IK 

i t)2 ir 



>1K» 



R3 
100K 



01 



S55 



1 



JTP 

i 



OUTPlfT 



FIG. 9— AN ALTERNATE VERSION OF 
OSCILLATOR shown in Fig. B. 

+ 5VrO + l5V 

; ^ 



C3 



B1 

2M 



D1 
1H4143 
— W— 



R2 
t.lK 



m 

IK 



R4 

75K 



555 



'Z^X T?! OUTPUT 



1 ' 



1 



FIG. 10— A PRECISION LOW-FREQUEN- 
CY OSCILLATOR with a frequency of 
aboyf 20 Hz. 

In the circuits of Figs. 6 and 
7, the width'to-space periods 
can be independently varied 
over about a iOO:i range, en* 



abiing the width-to-space ratio 
to be varied from 100:1 to 1:100. 
The oscillation frequency varies 
as the ratio is altered. 

Figures 8 and 9 show alter- 
nate ways of connecting the 555 
in the astable mode so that the 
width-to-space ratio can be var- 
ied wiliiout altering the oscillat- 
ing frequency In those circuits, 
the pulse width period automat- 
ically increases as the space 
length period decreases, and 
vice versa. Therefore, IItc total 
period of each operating cycle is 
constant. In those circuits* the 
feature of interest is the duty 
cycle, in Figs. 8 and 9, the duty 
cycle can be varied from 1% to 
99% with potentiometer R3. 

in the circuit of Fig. 8, CI al- 
ternately charges through RK 
the upper half of R3. and Dl, 
and It discharges through D2. 
R2. and the lower half of poten- 
tiometer R3. In Fig. 9, CI alter- 
nately charges through Rl and 
Dl and the right-hand half of 
potentiometer 1^3, and it dis- 
charges tlirough the left-hand 
half potentiometer R3, D2, and 



+ 5VTO+15VJ 



Rl 
IK 



,0t 



fl2 
75K 



555 



1 I 



I i 



1 



R3 



SI 



1 



OUTPtlT 



i 











1 r 






1 


ov; 


_ 


-■ 




























/. 






V 








1 













OUTPUT^ 
AT PIN 3 

txnpuT 

ACROSS 
CI 



--*KSt CLOSED 
$1 OPtfl 

b 



SI OPEN 



FIG, 11— GATED 1-kHz OSCILLATOR of- 
fering "press-to-tum-on'* operation, 
a, CFHB and waveforms at output of pin 3 
and across Cl^ 



+SVTO + ISV 



R1 
tK 



-01 



75K 



555 




I 



OUTPUT 



i 



OUTPUT 
J^PIN3 



SI CLOSED 
ft 



RG. 12— GATED t-kHz OSaLLATOR Qi- 
ferrng "press*to*turn-off" operation, a, 
and waveforms at output of ptn 3 and 
across Ct, 



m 



SS5 




OlfTPUT 




S1QfB« 



-$1 CLOSED 



SI 0PEI4 



RG. 13— ALTERNATIVE GATED 1-kHr 
OSCILLATOR offering 'press*to*turn* 
on'' operation, a, and waveforms at out- 
put of pin 3 and across CI, 

R2. Both circuits oscillate at 
about L2 kHz with the value of 
CI shown. 



Precision astable circuit 

In the description or astable 
multivibrator operation given 
earlier in this article, it was 
stated that in the first halfcj'ele 
of oscillation liming capacitor 
CI charges from zero volts to 
two-thirds of the supply voltage* 
but in all subsequent half-cy- 
cles it either discharges from 
two- thirds to one- third of the 
supply voltage or charges from 
one-third to two- thirds of that 
voltage. Consequently the first 
half cycle of oscillation has a far 
longer period than all subse- 
quent half cycles. 



ifSVTQ+ISV 
f f 



iWTO ♦ 15V 



(SEE TEXT) 



Rt 
IK 



6 



5S5 



R3 ^ 

IK |5 h 



CI ^ €2 I Qy-fp 



1 



OUTPUT 



OUTPUT 

ATpma 



^S1 aos€Dh- 



FIG, 14— ALTERNATIVE GATED 1-kHz 
OSCILLATOR offering ^ pre ss- to- turn- 
off" operation, Ta and waveforms at out- 
put of pin 3f t. 

In applications calling for a 
low- frequency clock signal, this 
large differential in period can 
cause a timing problem. How- 
even this problem can be aver- 
ted by adding an external 
voltage divider and diode as 
shown In Fig, 10. Those compo- 
nents bias CI to a point slightly 
below one- third of the supply 
voltage (rather than zero volts) 
at the moment of switch-on. 
Here. Rl rapidly charges CI to 
one- third of the supply voltage 
through Di at switch-on. and all 
of the CI charge is subsequently 
controUed by R3 and/or R4 only 








1 






































































— ■ 


















— siaostc ^ 





OPfH 



OUTPUT 



ourpuT 
Acnoss 



-SI OPItt 



FIG. 1&--PRECiSiON VERSION OF THE 
OSCILLATOR in Ffg. 13, and wave- 
forms at output of pin 3 and across 01, 



Astable gating 

The 555 in the astable multi- 
vibrator mode can be triggered 
ON and OFF in many different 
ways with either an elec- 
tromechanical switch or an 
electronic signal. The most pop- 
ular way to trigger the 555 is 
through re;skt f3in 4. Figures 
U-a and l2-a show alternative 
ways of triggering the 555 with 
this pin and pushbutton switch 
SL 

The 555 is organized so that if 
pin 4 is biased above about 0.7 
volts, the astable mode is en- 
abled. But if it is biased below 
0,7 volts by a current greater 
than 0-1 milliampere (by 
grounding pin 4 with a resis- 
tance less than 7 kilohms. for 
example) the astable mode Is 
disabled, and the 5551s output 
is biased low. 

For example, the circuit In 
Fig. 11-a Is normally turned off 
by R3, but it can be turned on by 
closing pushbutton switch Si, 
which biases pin 4 high. Figure 
12 -a shows an astable circuit 
that is normally on, but it can 
be turned off by closing push- 
button switch Si, which shorts 
pin 4 to ground. The circuits in 
Figs. 11 and 12 can also be trig- 
gered by applying suitable elec- 
tronic signals directly to their 



*5VT0+1SV 



R1 



.01 



R2 
75K 



555 



MODULATIDN 
INPUT 



I 



-O 

t 



OUTPUT 



i 



PULSE WIDTHS VARIABLE 



OV 



1 r 



Y 



4^ 



OUTPUT 
M PJfJ 3 



SlWCES EQUAL 



Fia le^iRCurr for applying ac- 

COUPLED FM or PPM to a 555 config- 
ured as an oscillator, a, and waveforms 
at output of pin 3, b. 




FIG. 17— CIRCUH FOR APPLYING A DC- 
COUPLED FM or PPM to a 555 config- 
ured as an oscillator. 




FIG. 18— CIRCUIT GENERATES SOO-Hi 
MONOTONE ALARM that operates rrom 
750-mllliwatts, 




^ 14- 



m ^ 



01 



03 



FIG. I^CIRCUIT GENERATES BOO-Hz 
MONOSTABLE ALARM. 



tion of CI and R4 close to zero 
volts through R2 preventing os- 
cillation. When pushbutton 
switch SI is closed. Q) is biased 
off, and the astable circuit is 
free to oscillate norinaUy* 

Refer to Fig. 13-b for the wave- 
forms of the circuit in Fig. 
When the astable response Is 
triggered on» the first half cycle 
is again considerably longer 
than in succeeding half cycles, 
and that the voltage on CI de- 
cays rapidly to nearly zero volts 
when the trigger is off. Also 
notice that output pin 3 is high 
in the off state. 

Figure 14 shows how the cir- 
cuit in Fig. 13-acan be modified 
to give pness- f o-furn-o/r oscilla- 
tion simply by replacing Ql with 
a pushbutton switch, A digital 
signaJ can trigger this circuit if 
a diode is connected as shown 
in the diagram and the push- 
button 51 is deleted. With SI re- 
moved, the circuit will be 
turned off when the Input sig- 
nal voltage is reduced below 
one- third of the supply voltage. 
The waveform is shown In Fig, 
14-b. 

Finally, to complete this look 
at triggering techniques. Fig, 




FIG. 20— CIRCUIT GENERATES SOO-Hi PULSED*TONE ALARM. 



RESET pins. 

In Fig. 11-b, the precise cir* 
cult waveforms at output pin 3 
and across CI are shown, it can 
be seen that the duration of the 
first half-cycle of oscillation is 
considerably longer than the 
succeeding half cycles because 
of the time for Cf to charge to 
two*thirds of the supply voltage. 
Also, note that when the astable 
mode is turned off, the CI volt- 



age decays slowly to zero: the 
output at OUTPUT pin 3 is zero 
volts in the off condition. The 
waveform characteristics of Fig- 
12-a are similar as shown in Fig. 
12-b. 

Figure 13-a shows an alter- 
native method for triggering the 
555 In the astable mode. Here 
transistor Ql is normally biased 
ON by RL so it acts like a closed 
switch, which pulls the junc- 



IS-a shows how the Fig. I3*aclr* 
cuit can be modified so that the 
duration of its first half-cycle is 
almost equal to that of all suc- 
ceeding half-cycles, thus giving 
precision operation. In the Fig. 
15-a circuit, when pushbutton 
switch SI IS open, Ql is satu- 
rated, so the voltage divider 
made up orR2 and R3 puUs the 
junction of R5 and CI to slightly 
below one- third of the supply 



^ — ^■ 



f 



f — 



R1 . 

iok: 



04 



R2 
75IC 



IC2 
S55 



CI : 

tOMF 



T 

T ^'T 

4 i 1^ 



lOK 



R4 

220K 



D1 
1N4D01 



R5 
OK 



it 










Z 




6 



IC1 
555 



C3' 
.01 



SPKR1 

8 a 



R6 



D3 4> 



FfG, 21^IRCUIT GENERATES WARBLE ALARM of European emergency vehicles. 



f- 



f T M- 



+ 12VTO + 15V 



R1 

4jK: 



:C3 



7 


















(► — 


6 



1C2 
555 



m 

TOK 



Dl 
1II40O1 



02 



1D0K 



^—7 01 



rci 

655 



IT 



R6 
2.7Kn 



R7 

1200 



SPKR1 



03 



02 
2H30S5 



FIG, 22— CtRCUrr GENERATES SIREN WAIL of poirce cars. 



— T ? — f f — f- 

R4 < 



i R2 



IC2 
555 



ft3 
12K 
01 

zmroz 



^ n SPKR1 

555 "1 ^ 



CT 



Z7K 



03 

03 47mF .01 " HI 

2113704 

i 4 — ^4 4 



R5 

lOK s 



t N- 



D2 
1N4Q01 



+ T2VTO+15V 



03 -- 
tN4Qai 



RS 
2011 



04 
1N4O01 



RG, 23.— CIRCUIT GENERATES PENETRATFNG ALARM of Star Trek spaceship. 



voltage through diode Dl, thus 
turning the circuit off. When SI 
is closed, Ql turns off. Dl is re- 
verse biased through R2, and 



the circuit is then free to oscil- 
late normaUy. 

Notice in Fig, 15-b thai when 
SI is first closed, CI starts to 



charge from an initial value of 
almost a third of the supply volt- 
age rather than from zero volts. 
Therefore, the duration of the 
initial half cycle is similar to 
that of all the succeeding half 
cycles. 

Modulation techniques 

All of the 555 astable circuits 
reviewed so far can be frequency 
or pulse-position modulated 
(FM or PPM) by Iceding a suit- 
able modulation signal to 
coNi ROL VOLTAGE pin 5, vvhlch is 
connected to part of the internal 
voltage divider chain of the 555. 
The AC modulation signal is fed 
to pin 5 through a blocking ca- 
pacitor, as in Pig, l6-a. or the 
DC modulation signal can be 
fed directly to pin 5, as shown in 
Fig. 17. 

The voltage on pin 5 of the 
Pig, 15-a circuit alters the width 
of the pulses in each timing cy- 
cle of the 555, but it has almost 
no effect on the space duration. 
The signal at pin 5 changes the 
PPM pulse width position, af- 
fecting the total cycle period so 
it also inlluences the output fre- 
quency, as showni in Fig, 16'b. 
In so doing, pin 3 provides a fre- 
quency-modulated signal- 
Those characteristics of the 555 
are useful for generating special 
waveforms. 

Alarms and sirens 

Some of the most popular ap* 
plications for the 555 organized 
as an astable multivibrator are 
as waveform generators for 
loudspeakers. They can pro- 
duce alarm and siren sounds. 
Figures 18 to 23 show difTerent 
wa>^ to create those sounds. All 
of the circuits in those figures 
are triggered by making or 
breaking their supply- volt age 
connections. 

Figure 18 shows an 800-Hz 
monotone alarm-call generator 
circuit, which can be powered 
by any 5- to 15-volt DC supply. 
The speaker SPKRl can have 
any impedance value. Note* 
however, that Rx must be wired 
in series with any speaker 
whose total impedances is less 
than 75 ohtns. Select a resistor 
to give a total series resistance 
with the speaker of 75 ohms. 

continued on page 94 



JAMES MELTON 



DO \X)U EVER NEED TO rO\V>:!^ 120 

volt ac equipment when there is 
no AC outlet available? Our af- 
fordable power inverter was de- 
signed to supply up to 250 watts 
lo power line-operated equip- 
ment a a fraction of the cost of 
commercially built units. 

The inverter described here 
has been used to power Hood 
lamps, soldering irons (both re- 
sistance and transformer 
types), fans, televisions, and 
portable computers. It has even 
powered an air pump for the au- 
thor's asthmatic son. The inver- 
ter will power almost any device 
that runs on 120 volts AC, Some 
motorized devices won't work 
well however* A variable-speed 
drill may work, but only at one 
speed. Fans and other purely in- 
ductive loads seem to run at 
about % normal speed with the 
inverter Synchronous motors 
will run at normal speed but will 
be a little "noisy/' 

Power FET's to the rescue 

Power FET (field eflect tran- 
sistor) devices have gotten more 
versatile over the last few years 
and, at the same time, the 
prices for them have plumm- 
eted. No tiling can match a FET 
in Its ease of interfacing with 
logic signals, and for the ease in 
which it can work in parallel 
with similar devices without 
the need for any extra compo* 
nents. To parallel the FET's. all 
you have to do Is tie the source 
leads togetlien When the they 
get warm, FET's exhibit a 
positive temperature charac- 
teristic, which means as the 
temperature goes up. so does 
the resistance: as the resistance 
goes up, the current through 
the device is lowered. That 
makes FET's self-limiting when 
working in parallel. 

FET's are now being produced 
with power ratings that can 
often make parallel operation 
unnecessary* The ratings for 
the 1RFZ30S that are used in 
this project are amazing: they 
can handle a SO-amp load with 
50 volts across the source-drain 
leads and 75-watt power dis- 
sipation, all in a TO-220AB 



plastic package — for less than 
two bucks each when pur- 
chased in small quantities. 

Operatioa 

Figure 1 shows the schematic 
of the Inverter, A 555 timer. ICl, 
along with R3. R2, and C2, gen- 
erates a 120-Hz ( ± 2 Hz) signal, 
as set by the value of potentiom- 
eter R3. 

The output of ICl at pin 3 is 
fed to the clock input of a 
CD4013BE dual D-type flip-nop. 
lC2-a. which is wired to divide 
the input frequency by two: that 
generatea the 60-Hp. clocking 
for the FET array {Q1^6), The 



output from nip-flop lC2-a at 
pin 1 has a 50% duty cycle, 
which is necessary for the out- 
put LransFormer, Tlie nip-flop 
also provides an inverted out- 
put (Q, pin 2), which saves us 
from having to add additional 
components to invert the q 
output. The second half of IC2 
(iC2-b) is not used, so all of its 
input pins are grounded. 

The Q and g outputs fmm 1C2- 
a are each fed. via R5 and R4, to 
three inputs of IC3, a CMOS 
CD4050BE hex buffer. Each 
group of three buffer outputs 
drives one bank of FETs in the 
power stage. 



Power small appliances from your 
car or any other 12'Volt source 
with our 250-watt inverter. 

250 WATT 

POWER 

INVERTER 




ri 

20 MIPS 



C2 



, 02 
1K4751 

13V 



D1 
tN4D01 
1 ^ 



S> 



Si 



^SQUARE WAVE) 



m 

33K 



R3 

50K 




a 



DISCHARGE 

ICI 
555 

THRESHOLD 
TRIGGER 



HItSET 

-^CLK 
0 

dciR 



- CB4I]13BE 

Q 
0 



R5 

4.7K 



V4 CtMOSQBE 



< SET ^Q2-b 



11 



10. 



CLK "'^ 



-C CLR 



R4 

4:7K 



05 
1H314 



Qt 
IBFZ30 



02 



03 



06 
1KSU 



Q4 



Q5 



06 

mFZsa 



7 Ii4r^i5 

i C04050BE 




D4 

tmm 



D3 

— H— 



FIG. I'-INVERTER SCHEMATIC. A 555 timer (ICI) generates a 120-H2 signol that is fed 
tea CD4013eE flip-flop (]C2-a} which divides the Input frequtncy by two to generate a 
BO-Hz clocking frequency for the FET array (Q1-Q8). 



The Inputs to the buITers are 
also controlled by D5 and D6, 
which are connected to the drai* 
ns of the FETs so that the array 
that is turned-on essentially 
heis control of the drivers of the 
opposite array* When one side Is 
turned on arid lis drain Is at 
ground potentiaK the other side 
cannot turn on because the in- 
put to the buffer for that array is 
also being held at ground. It 
stay^ that way until the control- 
ling array has completely 
^ turned off and the drain voltage 
a has gone above about 6 volts. 

That is necessary because the 
o turn-off time for a FET is longer 
S than Its turn-on time. If the di- 
g odes were eliminated, both ar- 
z rays of FET's would be turned 
3 on simultaneously during each 
o trans ist ion. which creates tre- 
B mendous spilies on the battery* 
m the equipment tied to the out- 
put of the inverter, and to the 
76 FETs themselves. 



The FET array can be made as 
big or as little as your applica- 
tion requires. The author 
needed at least 250 watts, and 
used two IRFZ30's in parallel for 
each array. Howevcn to play it 
safe, use three in parallel (or 
however many you need| for 
each array as we ve shown In 
the schematic- Diodes D4 and 
D3 dampen Inductive kickback 
from the transformer winding 
that would likely cause over- 
heating and premature tran- 
sistor breakdown. 

Power-supply conditioning 
circuitry (Dl. RK D2. and CI) 
eliminates spikes, overloads, 
and other noise from a cars 12- 
volt supply. Even though the 
555 can handle up to a 15-voli 
supply, power-supply spikes will 
surely damage it. 

If the transibrmeryou use has 
a center tap. the center tap must 
be connected to the 12- volt line 
and the two 12-volt windings 



must be connected to the drains 
of their respective driving tran- 
sistors. The author used a 
Jefferson buck/boost trans- 
former that's normally used to 
reduce or increase the line volt- 
age for AC devices. If you are 
going to buy a transformen you 
can use any center-tap 24-volt 
or dual-winding l2-volt trans- 
former. It is important to use a 
transformer that can supply tlte 
ammount of current that your 
application requires. 

Construction 

Some of the components 
mount on a small PC board, for 
which weVe provided the foil 
pattern. The parts-placement 
diagram is shown in Fig. 2. We 
recommend that you use sock- 
ets for the ICs. After soldering 
all components on the board, 
apply 12 volts and measure the 
frequency on the pads marked 
J4 and J2. Adjust R3 for a read- 



120 OUT 
fSOUARE WAVE I 



; WINDING TWO 
♦ 



\ r # 

; g WiNDIKGOfJE 











n r n n 









" ri 



05 

lb A 



I i 

| 3 D IS R n w n 

) IC3 

^ s B [3 ^1 rr 



J2€ 

JSC 



) fCT 

ri r n 



T r 

R3 fl2 CZ 

i 1 



0>i 



05 



06 



D3 



, I OT 02 T 03 



ct 



D2 




Fia 2— MOST OF THE COMPONENTS mount on a small PC board. The off^board 
components can be mounted on a terminal strip of perforated construction board. 



ing of 60 Hz, and make sure the 
voltage is very close to Vi o{ the 
supply voltage on each pad. 
That tells you that your dutv cy- 
cle is 50%. 

Now connect the rest of the 
components. The small off- 
board components can be 
mounted on a terminal strip. 
However, be sure to mount the 
FETs on a heatsink. If the heat- 
sink is at ground potentiaL also 
be sure to insulate the FETs 
from it. 



^^^^^^ 




1^ 

X 



FOIL PATTERN for the Inverter board. 



PARTS LIST 

All resistors are Vi-watt, 5%, un- 
less otherwise noted, 

Rt— 60 ohms. 1 watt/10% 

R2— 33.000 ohms 

R3— 50.000 ohms. 10-tum potenti- 
ometer 

R4, R5-4700 ohms 

Capacitors 

CI— 220 35 volts, electrolytic 

C2— 0.1 50 volts, ceramic cfisk 

Semiconductors 

1C1— LM555 timer 

102— CD4013BE CMOS dual D- 

type flip-fJop 
ICS— CD4050BE CMOS hex buffer 
D1, D3, D4— 1N4001 diode 
D2— 1N4751 IS-volt Zener diode 
D5. D&-1N914diode 
Q1-Q6— 1RFZ30 30-3mp, GO^volt 

FET 

Other components 

Tl— Jefferson #216-1121 buck/ 
boost transformer (contact WW 
Granger. Inc., 1250 Busch Pkwy. 
Buffalo Grove, IL 60015, 
708-459-5445} or other 12- or 24- 
volt center-tapped transformer 
(see text) 

SI— SPST switch 

F1 — 20-amp fuse (or use value ac- 
cording to desired oLftput cunent 
and transformer used) 

Miscellaneous: fuse holder, cab- 
inet, mounting hardware, AC out- 
let, car cigarette lighter plug, wire, 
solder, etc. 




FIG. 3— THE PROTOTYPE INVERTER. 
The author used a car cigarrette lighter 
plug on the end of the power-input lead 
and an AC outlet for plugging appli- 
ances into. 



■Ik 



FIG, 4— THE FET'S ARE M0U^fTED on 
metal pfates used as heatsinks. If the 
heatsink Is at ground potentiaL Insulate 
the FETs from the heatsink. 

The author used a car ciga- 
rette lighter plug on the end of 
the power-input lead, but you 
are free to use aUigaior clips or 
whatever is most convenient for 
you. A stand^ird AC outlet was 
mounted on the front panel of 
the unit. The prototype was in- 
stalled in an old, rugged metal 
case, but you can use whatever 
you have on hand. Figure 3 
shows the prototype inverter 
and how everything is as* 
sembled. Figure 4 shows a 
close-up view of the FETs and 
how they are mounted on metal 
plates used as heatsinks. 

Operation 

lb operate the unit, plug the 
input power into your cigarette 
lighter socket, turn on the 
I>ower switch, and turn on the 
appliance that's plugged into 
the inverter When you are not 
using the inverter be sure to 
turn it off, since the trans- 
former will draw about 2 amps 
even with no load. That will 
drain your car battery fairly 
quickly! R-E 



AUDIO UPDATE 



Syndicated Reviewers, AM Stereo, and Consumer Fraud 



LARRY KLEIN 



I've frEquently been dislrBSsed 
by the writings of the syndicated 
audio columnists, the pundits 
whose opinions appear weekly in 
large and small local newspapers. 
IVe met nr^any of them over the 
years and. by and large, they are 
nice people, but I just don't like the 
job they do. What's wrong? Several 
things. 

I feel stnongfy that a writer should 
not express his opinion in print on 
the audio qualities of a borrowed 
product listened to under uncon- 
tnolled conditions in a home environ- 
ment. Such home evaluations 
without lab test backup are, in gen- 
eral. untrustworthy. They actually 
teJl you far more about the writers 
mood, health, and relationship with 
the manufacturer than they do 
about the product. This is not to say 
that some of the recommended 
products aren't topnotch, but the 
reader has no way — sound un- 
heard—of confirming the reviewer s 
opinions. 

Am I being loo harsh in my judg- 
ment? I think not. The temptation to 
say nice things about a product be- 
comes intense when a writer has 
been personally wined, dined, 
junketed, and brainwashed by a 
company's public relations agency 
I can say that in the 35 years or so 
that I've been writing atx>ut audio 
I've kept my skirts relatively clean. 
Despite temptations to do other- 
wise, I have never confused my sub- 
w jective opinions with objective facts 
S and never praised a hi-fi component 
i In print without a lab test backup. I 
5 should admit that as the technical 
O director of the worid s largest cir 
I" culation audio magazine, 1 found it 
^ easy to be hoJter than almost any- 
"p body t regulariy received such man- 
S ufacturer-supplied perks as all- 
S expense-paid annua! trips to audio 
shows and factories in Japan, Eu- 
78 rope, and elsewhere, and all the 



long-term-loan audio equipment I 
could use without extolling the vir- 
tues of anyone's products. Free- 
lance writers, on the other hand, 
inevitably find themselves in a quid 
pro quo situation. The amount of 
laudatory "ink" they give to prod- 
ucts in their columns correlates di- 
rectly with the frequency of invites 
to press junkets. Their columns and 
comments are reprinted by gratified 
manufacturers, and they are on the 
"A" lists for goodies. 

Once I left SterBO Review for the 
freelance life, my invitations slowly 
dwindled as the various PR agen- 
cies became aware of my new unex- 
alted status. I could have reversed 
the situation somewhat by taking 
the same product review route as 
my syndicated contemporaries, but 
I chose not to do so. In any case, to 
reaffirm my point: Be careful before 
committing your dollars on the basis 
of any opinions unsupported by lab- 
oratory testing. Its just too easy to 
be mislead. 

AM stereo 

Remember AM stereo? it s an 
idea that won't die — but won't 
come fully to life either Perhaps a 
dozen years ago, when AM stereo 
was first introduced as a new broad- 
cast technology, I wrote that be- 
cause of the lack of consumer 
interest the format would probably 
never fly. The letters of drsagree- 
ment that subsequently reached my 
desk were mostly from station 
owners, broadcast engineers, and 
companies with investments in AM- 
stereo technology. 

For years there was no visible 
pnDgress on the AM-stereo front, 
possibly because the FCC in its 
wisdom Cha!) decided to let the 
competing formats fight it out in the 
marketplace. True, there was an oc- 
casional press release telling of this 
or that company's home or car re- 



ce'rver*s having AM-stereo recep- 
tion facilities, usually Motorolas 
system. 

A mini breakthrough almost oc- 
curred in June 1990 when the Na- 
tional Association of Braadcasters 
(MAS) and Denon announced a 
"comprehensive component broad- 
cast monitor tuner that does it all." 
The "air* included the now-defunct 
FMX FM noise-reduction system. 
AM stereo (Motorola "s C-Quam). 
and the newly promulgated NRSC 
AM standard. The new standard in- 
cluded an extension of the AM tun- 
ing range (520 to 1710 kHz), a pre- 
emphasis/de-emphasis curve, and 
a vsrtden lightiy specified audio band- 
width. The tuner was pnDmised for 
"eariyl991."" 

I recent!y called the Denon tech- 
nical rep to ask what, if anything, 
had happened to the tuner He faxed 
me a copy of a press release dated 
May 1992 announcing a revised 
tuner that no longer had FMX but 
did have AM AX. which seems to be 
the NRSC parameters under a new 
name (See Radio-Electronics, 
February 1992 for more details). The 
AM bandwidth can be switched to 
wide or narrow, providing either the 
broadest audio-frequency response 
or the lowest noise. Helping to re- 
duce AM impulse noise is a notse- 
btanking circuit from Sprague/Alle- 
gro Microsystems. 

1 found the tuner s technical spec 
sheet, which was printed in Japan, 
to be somewhat puzzlmg. The audio 
frequency response of the AM 
tuner set to wide is given as 50 Hz 
to 7,5 kHz, +1.5 -3 dB. Certainly 
that s better than what one finds in 
most AM/FM receivers, but it falls 
far short of CD quality. 

The claim has been made that 
good AM stereo is frequently indis- 
tinguishable from FM. That may well 
be, given the aging ears of the clas- 
continued on page 96 



HARDWARE HACKER 



Histogram equalization, alternate action latches, gamma curve 
correction, digital image processing, and semiconductor IC houses. 



DON LAHCASTER 



Stop the presses. Murata has 
jusl announced a Gyrostar 
piazo gynDScope. Which, rf it 
rs as gmat as it looks, coufd easily 
beconne the hacker component of 
the decade. All I've got on this so far 
IS that brief note in the June 8th 
Design News and a promise for 
more technical information. Need- 
less io say the hacker potential of a 
$5 navigation gyro would be truly 
revolutionary. 
Be sure to stay tuned on this one. 
Things are also starting to happen 
fast and furious on that direct'toner 
printed circuit board front. Since my 
last report, the new water-soluble 
decal-based Toner Transfer System 
offered by Dy^iaArt has been further 
improved. The new Printed Circuit 
Board Transfer Film from Techniks 
looks even nnore promising. 

What Techniks did was take their 
old differential transfer system and 
add a new blue polymeric release 
coating. The polymeric release 
coating can dramatically improve 
the transfer: it actually becomes an 
important part of your resist pattern. 

Faster than light? 

Every week or so I get at least 
one letter or helpline call from peo- 
ple who feel they have clearly 
broken some physical law. Maybe 
they have proof that the speed of 
light is not a constant. Or that those 
three laws of thermodynamics just 
do not apply to them. Or that per- 
petual motion can be possible using 
magnetic repulsion. Or they have 
lapped the zero point scalar energy 
from the fabric of space. Or that 
their latest pet theory pru\^s the 
cold-fusion process, 

Usually, they'll also complain that 
they've sent their theory every- 
where and have gotten no replies. 
Or that th^ arB getting ignored be* 
cause they are outsiders. 

Very often, their inquiries will be 



self-defeating. How? They will in- 
clude totally irrelevant religious or 
political contexts. Or they* II be 
super secretive. Or written and sub- 
mitted in such a way that they 
scream "Hey, kick me. for Tm not 
even computer literate/" 

If it likes water looks like a duck, 
and quacks like a duck... 

But consider who is receiving 
those letters. Based on past experi- 
ence, the editors or the publishers 
know that the probability is 0.99 H- 
that the lab work Cif any) is just plain 
wrong. Or more typtcally not even 
wrong. And 0,99 that the sendee 
is clearly a few chips shy of a fult 
board. Why should they believe 
you? 

The sad thirig is that needle in the 
haystack. Tm going to be generous 
and claim that one letter in 500 in 
fact does have the germ of a new 
theory or a developable product or a 
fresh look at a solvable problem. 
And, yes, newer ideas often will get 
ignored or vehemently attacked. 

What can you really do if you have 
genuinely beaten those overwhelm- 
ing oddsandyour controversial idea 
is in fact both new and for real? 

There are tvw3 possible routes you 
could take to get your ideas accept- 
ed. The first or mat science method 
is to thoroughly try and pra^ that 
you are wrong. Be sune to use lots of 
careful research, especially through 
Dialog and those UMI reprints. Be 
certain to subscribe to all of the rele- 
vant insider trade journals and go 

NEED HELP? 

Phone or write your Hardware 
Hacker questions directly to: 

Don Lancaster 

Synergetics 

Box 809 

Triatcrier. AZ 85552 
(602) 428-4073 



out of your way to study the schol- 
arly publications in the field- Learn 
all the lingo. Attend conferences 
and trade shows. Find a patient and 
knowledgeable industry insider that 
is willing to look at your idea and 
comment honestly on it- 

Be absoiutety certain that you 
have B simple experiment that can 
be independently duplicated and 
verified by disinterested outsiders. 

Hire some competent engineer- 
ing or physical science consultants 
to study and add credibility to all 
your claims. Take enough college 
and university level courses to make 
sure you do thoroughly understand 
at least the fundamentals of the 
field — along with the needed math 
to back it up. 

And finally* present the ideas 
clearly identified as a possible new 
theory tn some professional context 
totally free of religious* polittcai or 
any conspiracy mumbo jumbo. 

The second route is to publish via 
a pseudoscience press. There are 
quite a few underground and alter- 
nate life publications that welcome 
materia! of this type. Every now and 
then. Whole Earth Review gives you 
a list and rundown of all the maga- 
zines of that genne. Let me know if 
you want to see a resource sidebar 
on those. 

One leading bookstore that does 
specialize in selling and distributing 
pseudoscience topics is High Ener- 
gy Enterprises. Many of their offer- 
ings are utterly fascinating. Those ^ 
folks also sponsor several yearly ^ 
forums where controversial ^ 
pseudoscience topics are strongly g 
encouraged- 

Several very important tips when |" 
publishing your own pseudoscience g 
tracts: Be sure to use cut-and-paste b 
Xerox*of-a*Xerox and lots of poorly ^ 
printed sloppy layouts. Smeared ink 1 
on cheap paper is a must. Freely 
quote obscure rural newspapers as 79 



your prime data sources. Include il- 
legible artwork. Extensively refer to 
unheard-of and unavailable ioumals. 
Use plenty of irrelevant inference 
and innuendo. 

Use only 20-200 year old refer- 
ences, especially in any rapidly 
changing field. Misquote and drop 
some big names, even if totally out 
of context and they never heard of 
you, "Billions and billions of Carl 
Sagan's ago..." Never offer any 
succinct and easily van f ted experi- 
ment. 

Always use ten words where one 
will do. Make alt of your paragraphs 
unbearably wide and long. Then run 
them all together rn haphazard 
order. Never come right out and 
state your key points. Work Tesia in 
somehow, and be sure to include 
plenty of obscure religious and/or 
political references. Show how your 
theory is now being suppressed by 
a federal conspiracy headed by the 
Trilateral Commission and secretly 
funded through both the WCTU and 
the SPCA, 

Ignore all the personal computers 
entirely They are only a passing fad 
that never will catch on, Finaliy do 



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(A) Relay convertecf to latch. 




> I- 

i Clear JE. Set 



(B) Inverter pair used as laicfi. 




{C} Alternate action pushbuLlpn. 



FIG. 1— SOME SIMPLE UVTCHES and 
alternate action circuits. 

not ever, untder any circumstances, 
use any new desktop publishing 
tools and techniques. 

Alternate action switches 

I got a helpline call the other day 
asking For a circuit to convert any 
old ordinary relay into an aiternate- 
action on-off device. Well, as the 
caller has found out on his C3wn, that 
gets a little tnckier than it sounds- 
Figure 1 -a shows how to convert a 
regular relay into a latching relay. 
Press normally open button A and 
your relay pulls in. The pull in closes 
a relay contact that holds the relay 
engaged. To reset the relay, pness 
normally closed button B. The relay 
dn^ps out, opening its latching con- 
tact. This IS a simple example of a 
latch, or a set-reset flip-flop. 

In Fig. 1-b we've used a pair of 
digital logic inverters instead. An in- 
verter outputs a one for any zero 
input and vice versa. Assume the 
left inverter happens to be output- 
ting a one. The hght inverter sees 



this one as an input, and outputs a 
zero. The zero in turn reaches 
areund and holds the left inverter in 
its present state. We are thus 
latched and stable. Press button A 
to set your latch. P^ss button B to 
clear your latch. 

It turns out that any altemate*ac- 
tion circuit has to consist of (wo 
distinct storage elements. One is 
for "Where am I?" and one is for 
"Where was I?" If you don't provide 
two storage devices, you will get 
into major reliability, oscillation, or 
prefenred state hassles. 

In most integrated circuits, the 
two needed storage elements are 
done with a pa/r of separate latches. 
One is called the master flip-flop. 
The other is the slave flip-flop. Often 
they are combined into a single 
more complex logic block, forming a 
type-D clocked flip-flop or some 
similar device. 

Check carefuify, and you will even 
find that the button on a retractable 
ball-point pen consists of two dis- 
tinct storage devices. 

The simplest alternate-action 
pushbutton I know of appears in Fig. 

The "Where am I?*' storage 
consists of that pair of back-to-back 
inverters. The "Where was I?" stor- 
age is the capacitor. 

Here s how it works: Some brief 
time after that latch changes, the 
capacitor will charge up to hold the 



The VALUE at eadi PEL or pictuia elemant 
det&rrntnos Ihe brightness for thai pel; the 
tOCATtON of that pel In the array sets 
til a pel position in your actuai image. 




107 aOG 035Tiri93 2S4 - 091 

080 12a £19(l3)l77 161 ■ £53 

101 223 115 216 01S 041 - 251 

OaS 205 001 240 032 089 - 093 

032 093 170 079 093 106 ■ ■ 115 

119 023 126 194 091 086 ■■ 004 



FIG. 2— A DiarrAL IMAGE Is noth{n9 but 
an array of numt:t^rs. Digital image pro- 
(jessing takes those numbers and re* 
places them with other numbers, 
foJ lowing a ru[e or set of rules. While 
there ts a stunning variety of uses for 
digital image processing tricks and 
techniques, two of the most important 
involve gannma correction and hlsto* 
gram equatization. 



f 



SYNERGETICS 

Box e09-RE 
Thfitchor* AZ 65552 
(602) 428*4073 



(K) Typical Gamma curve of a CRT electron beam 
cJispiay or a 'white write* laser printer witl 
wash out many of the lighter whites* 

(B) Properly gamma correcled display or printer 
treats alt gray levels equally. Some available 
gray levels may be lost In the process. 

(C) Typical Gamma curve of a 'biack write" laser 
printer (such as a Canon SX) wilt muddy the 
darker grays. 



(white) 



Perceived 
gray levels 
at output 



(black) 




Intended gray levels at input 



RG, 3— THE GAMMA CURVE for any display or printer relates how the brightness 
levels are viewer perceived compared to how they are input. A non-linear gamma 
either '^muddies the lows" or "washes out the highs/' Gamma correction attempts to 
make each gray equally significant to the end viewer. 



''Where was I?" one or zero. Press- 
ing the button forces the "Where 
was I?" value back onto the input of 
the first inverter, and the latch quick- 
fy flips. 

That happens because the 
charge on a capacitor cannot 
change immediately. Thus, at the in- 
stant the switch is closed, the ca- 
pacitor acts as a very low 
impedance which "force feeKis' its 
value to the inverter input. As soon 
as the inverters flip, positive feed- 
back reinforces and holds the new 
value. 

Releasing the button will let the 
"Where am I?" pair of inverters 
work normally A short inters^! later, 
the capacitor will charge up Cor 
down) to its new "Where was I?" 
value, and the cycle can repeat. 

The circuit can also be used as a 
relay driver It's the fastest and best 
way I know of to make a mechanical 
relay reliably alternate its states. 
While any old CMOS gates could 
be used, my favorite here would be 
a 74HC13 hex Schmidt trigger 
Much mom technical information on 



counters , latches* and state alterna- 
tion appears in my CMOS Cook- 
book, 

Digital image processing 

{ never cease to be amazed at 
how stunningly versatile that 
PostScript general-purpose lan- 
guage is. I've recently used 
PostScript to create a group of 
rapid, easy, and fun digital image 
processing tools. The tools and a 
few test images to go with them 
have been posted to my GEnie 
PSRT RoundTable as IMAGE- 
KIT.PS, 

What I'd like to do here is give you 
a brief introduction to digital image 
processing. We'll limit ourselves to 
high-quality gray-scale images. 

We will also try to zero in on doing 
both a gamma correction and a 
histogram equalization. Those are 
both highly important and little un- 
derstood cmcial uses for serious 
digital image processing. Fail to un* 
derstand either one and your im- 
ages will all end up as disasters 
waiting to happen. 



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We'll first note that good old sil- 
ver haiide "slopping-in-the-slush" 
photo work »s both incredibly ver- 
satife and highly forgiving — besides 
having an enormous dynamic range. 

Instead, electronic digital dis- 
p^ays. printers, and any photoset- 
ters demand data which is always 
'Vight on/' If anything misses at all. 
you will get lousy to useless results. 
That s why digital image processing 
has become so important. And so 
hackable. 

Hmmm. To do some digital image 
processing, you hav^ to start with a 
digital image. You can borrow one of 
mine off of CEnie PSFET, or grab one 
from a scanner, off a satellite, a fax 
nnachine, or a video-capture board. 
Such a digital image is made up of 
picture elements, or pels. Note that 
a pel may or may not be the same 
size as the final pixel on your output 
device, A pel is simply the minmum 
resotvabte data value found in your 
numbers within the digital image. 

In a gray scale image, a pel gets 
defined by three parameters. The 



pel tuminancB value wifi tell you how 
bright this tiny portion of your scene 
will be. Its X position value will tell 
you how far over in the picture this 
pel sits, while its Y position tells you 
how far up and down. 

Fennstance. in the LENAPS file 
#463 on up PSRT we use 256 pos- 
sible grays (ranging from 
PostScript sO = biack smoothly up 
on through a 1 = white). These pels 
are arranged as an image 256 bytes 
wide by 192 bytes high. That size 
was picked to be big enough to be 
useful and interesting, yet small 
enough, short enough, and fast 
enough to have lots of fun with. 
PostScript, of course, can handle 
any image size and resolution you 
want. 

The first byte in your data file con- 
tains the 8'bit luminance value for 
the upper lefthand pel. The second 
byte is for the next pel to the right* 
and so on. After 256 horizontal 
pels, the data starts over again at 
the left pel of the next line down. 
This repeats for a total of 192 lines 



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or 49152 bytes. Or 48K for short. 

As Fig, 2 shows us. digital in»age 
processing simply consists of tak- 
ing this large array of digital bytes 
and then creating a second array of 
new digital bytes. The bytes in the 
second array are related to the 
bytes in the first array by some rule 
or set of rules. And your processed 
new image should somehow be 
"belter" for whatever you are trying 
to do. 

For instance, we nnjght just take 
each individual data value and make 
It larger That would bnghten your 
display and give you //g/?fer values. 
Make each data value smaller, and 
you will instead darken your display, 
favoring darker values. 

Should there be any defect in the 
picture, you can "retouch" by look- 
ing at adjacent pel values and work- 
ing out some type of average. 
Canned to extremes, this sort of dig- 
ital image processing can fBmove 
telephone poles from pictures, rear- 
range trees, and literally leap tall 
buildings with a single bound. 



A digital fmage processing anti- 
aliasing tnck lets you remove the 
jaggies from black and white lines. 
For antialiasing, gray values should 
get substituted equal to the ex- 
pected average value at each pel 
From any reasonable viewing dis- 
tance, your jaggies will magically 
disappear 

Calculating new pel values based 
upon values of neighbor pels opens 
up all sorts of powerful digital image 
processing opportunities. Ferins- 
tance. if you average or Icw-pass 
filter against nearby pels, you can 
soften or soft focus your image. If 
you emphasize differences, you can 
cnspen or sharpen your final image. 
Carried to extremes, a crispentng or 
sharpentng becomes edge detec- 
tion, where only outlines remain. A 
magic algonlhm called a Laptacian 
is often used for htgh quality edge 
detection. 

What if your onginal picture is out 
of focus or blurry? Well, you can go 
to a rather fancy Fourier or wavelet 
transform into a transform plane 



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Gray levels Gray 

FIG. 4— THIS STOCK 'LENA" DIGITAL IMAGE appears rather FIG, 5^HIST0GRAM EQUALIZED 'LENA * DIGITAL IMAGE has 

'"weak" or "low in contrast.'* A glance at the histogram clearly muchhlghercontrastThehistogram shows all gray values are in 

shows why. There are no dark blacks, no tighter whites, and the full use. A full histogram equalization Is the equivalent of a 

few remaining grays cluster around the two peaks. perfect photo darkroom 'dodge and burn." 



and extract a debluning function. 
Which can cancel out much (but not 
all) of such things as camera mo- 
tion. And perform such tricks as 
reading those license plates on 
speeding cars. 

There are now zillions of exciting 
techniques which use digital image 
pnocessing. We may look at some 
of these in future columns. But the 
first of the two techniques I feel are 
by far the most rmportant involves... 

Gamma correction 

The eye acts as a fog, rather than 
a linear device. And deep down in* 
side, most display schemes are also 
quite nonfinear As Fig. 3 shows us. 
^ the Gamma curve for any imaging 
system nefates how the expected 
^ input gray levels actually appear to 
g your eye at the output. 

The process of "fixing" a gamma 
J curve is called Gamma Correction, 
g On a video display, nonfinearities 
I are purpose// introduced to attempt 
g to cancel out such nonlineahties as 
iij the square law response of most 
electron beams to a control voltage. 
84 In color work, the strengths of each 



individual beam are also carefully 
adjusted to make each color appear 
to be equally bright. Even if the color 
phosphors used have different sen- 
sitivities. As does your eye. 

If at all possible, you want to do 
your gamma cormction in some way 
that does nof cut into the number of 
grays you hav^ available. But if it 
simply can't be helped, digital image 
processing can be applied lo gam- 
ma correct your display. It can do 
that by redefining gray levels, trad- 
ing off a lot of nonlinear grays for 
fewer and more linear ones. 

All of today s laser printers have 
inherently nonlinear gamma curves. 
This happens because a n^und dot 
is used which has to be larger than 
the intended square prxel it is sup- 
posed to completely and flawlessly 
cover. Thus, in a black write system 
(such as the Canon SX) where the 
laser places down black dots, typ* 
ica! gray levels usually end up darker 
than you asked for 

The PhotoGfsde system used on 
the Apple LaserWriter G uses dig- 
ital image processing to trade off its 
gray levels for a more linear gamma. 



We saw some details on the 
PhotoGrade halftoning prcjcess last 
month. At 106 DPI. Apple's Pho- 
toGrade system has 128 gray levels 
available. A total of 6t of these are 
often used for gamma correction. 
The gamma correction redefines 
lots of realty dark grays and a few of 
the mtd range grays. The net result 
is the remaining 67 distinct and fully 
Gamma corrected grays. 

The PhotoGrade system offers 
you three calibration options. The 
options compensate for your par- 
ticular choice of toner, density set- 
tings, humidity, and so on. On a 
calibration^ a coarse and a finer half- 
tone square are put down for typical 
gfBy levels. This is done for three 
different pages. You then pick the 
page you like the best. The internal 
code does a predefined Gamma 
correction for you. 

Additional details on PhotoGrade 
processing appear in my GEnie 
PSRT#451 LASGCAL.PSandover 
in #388 Li^SGNOTE.TXX Also 
quite handy is a #R023il/A 
LaserWriter tfg hinters D&mioper 
Notes from APDA. 



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Histograms 

Those photo darkroom techni- 
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tricks they use to explore the in- 
credible dynamic range of photo 
film. By lengthening or shortening 
all their exposures, they can make 
all of their prints darker or lighter By 
pnnting on a "soft" paper, they can 
reduce therr dynamic range and 
contrast. Or increase it by using a 
**hard'' paper Or eliminate it entirely 
with a "litho" photo paper 

Even moiie sneaky is dodging and 
burning. With dodging, you put your 
moving and out-of-focus hand or a 



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dodging paddle between the en- 
larger and the area bemg printed. 
That holds back your light in a se- 
lected area and nnakes that area 
lighter than nornnal. Which lets you 
pull details out of any dark or "mud- 
dy" areas of your negative. 

With burning, you hold an opaque 
mask having a small, ragged, out of 
focus, and rapidly moving hole in it 
between your enlarger and the print 
paper. Burning lets you darken your 
highlights and extract details from 
underexposed areas. 

By now. most of you have seen 
those spectacular Navajo slot can- 



yon photos. Most any southwest 
calendar should include at least one 
example. And Arizona Highways wHI 
be happy to sell you bunches of 
them. These mcnedible prints cany 
dodging and burning to an extreme, 
using multiple exposures and twen- 
ty or more very preciseiy aligned 
dodging masks to bring out the sub- 
tleties of color and texture. 

Digital image processing can be 
used to imitate these darkroom 
tricks. And gettmg things right on 
gets even more important with dig- 
ital images, because you will alv^s 
be severEly limited by both the dy- 
namic range and laser resolution. 

The fii^t step in correcting a dig- 
ital image is to find out what was 
wrong with it in the first place. To do 
this, you run a histogram. A histo- 
gram is simply a vote on how many 
of the grays get used how often. 
Figure 4 shows us the stock and 
welhknown Lena digital image, 
which should appear slightly 
'weak'' or low in contrast. 

That histogram underneath Lena 
cleariy shows us why. Those light- 
est and darkest grays are not used 
at alL And most of the rest fill two 
cleariy defined peaks. 

A digital image processing meth- 
od known as histogram equalization 
will let you perform a magjc dodging 
and burning that can often dramat- 
ically improve your results. In Fig. 5 
you see a much higher contrast and 
greatly improved Lena with lots 
more *'snap." 

To do your histogram equaliza- 
tion, you try to spread all of your 
pels around such that each gray 
gets used nearly as often as any 
other. You can then selectively re- 
place each pel with a lighter or a 
darker gray, adjusting your accumu* 
laled sum to spread out the total 
number of pets per gray. 

In short* you 11 do an absolutely 
perfect dodge and bum. § 

For instance, if you have 49152 S 
pels in your image and use 256 gray ^ 
levels, you redefine your grays to ^ 
get about 192 or so pels per gray 
level. A simple accumulated running ^ 
average does the job for you. Full a 
code details in my digital image g" 
tools on GEnie PSRT especially IM- ^ 
AGEKITPS. As you can see in Fig, i 
5. nearly all of those available grays 
are Fully and uniformly used. as 



By doing a histogram equaliza- 
tion, you can pnnt "auto shopper" 
quality images on any unenhanced 
300 DPI laser printer 

Figunes A and 5 are available as 
PSRT files #463 LENA.PS and my 
#468 LENAHIST.PS. 

Semiconductor chip houses 

I have been meaning to do some 
resource sidebars that give you 
most integrated circuit manufac- 
turers, or at least the more hacker- 
friendly ones. Since there's so many 
of them. weHI need several sidebars 
to do the job right. So, Acfe/ through 
Fujitsu will appear this month, and 
I'll show you the fBSt of them as we 
get to them 

Some data books are free. 
Others have "optional" pncing de- 
pending on whether the sales per- 
son likes you or whether any of the 
covered chips are currently being 
promoted. For others, just about ev- 
erybody has to pay the going rate. 

Your best bet is to first request a 
short fomi catalog, a price list, and 



their technical literature and applica- 
tion note rndex. These are all usually 
both Free and Immedrately available. 

Be sure to use your laser-pnnted 
letterhead or a professional sound- 
ing telephone request. 

New tech lit 

Data books include the 
Optoelectfomc Products Catalog 
from Quality Technologies. This 
used to be the old GE/Harris opto 
line. 

Advanced Lmear Devices has a 
f^duct Databook on linear timers, 
op amps, and comparators. 

From Signettcs/PhiUps. there's a 
new data book on CMOS Se- 
quencer Solutions. And from 
Hitachi, there's a Semiconductor 
Devices for Communicattons data 
book. Included are lots of telco and 
cellular radio devices. 

Our two brand new labor-of love 
newsletters include WeatherSat Ink 
and the Geo-Monitor The first is on 
weather satellite image reception; 
the second on earthquake monitor- 



ing and prediction. 

Over tn our neat mechanical Stuff 
department, a fiee sample of a laser 
machined plastic ts available from 
KMC And an rncredible catalog 
fnDm Outvoter Plastics. These folks 
are labonng under the delusion that 
they are now in the store display 
fixtures business. In reality, they of- 
fer lots of useful new electronic and 
prototyping hardv^re at unbeatable 
prices. Not to mention off-the-wall 
ideas. They even stock Grecian urns 
for writing odes on. 

For the two key books on all of 
the fundamentals of digital inte- 
grated circuits, try my CMOS 
Cookbook and JTL Cookbook, ei- 
ther by themselves or as part of my 
Lancaster Classics Library. 

As usual, we've gathered many of 
the resources mentioned together 
into either the Names & Numbers or 
the Integrated Circuit Manufac- 
turers sidebars. Check these out 
before you use our no-charge tech- 
nical helpline or call for your free 
hacker secrets brochure. 



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Let's see what's involved in desc rambling a SSAVI signal. 



ROBERT GROSSBLATT 



Fooling around with the simple 
video stuff we*ve been build- 
ing is a nice afternative to 
hanging around on street comers, 
but it s not really all that terrific if 
your ultimate goal is to figure out 
what to do with the junk that shows 
up on certain channels on your TV. 
Suppressed sync is the Modei-T 
version of video scrambling, and 
you can bet your bottom dollar that 
things have gotten a tot more com- 
plicated. Enter the digital age. 

Since the suppressed-sync 
scrambling system was so simple, it 
wasn't long before people with only 
moderate electronic skills figured 
out what was being done and how to 
beat it. Even the simple stuff we put 
together over the last couple of 
months could—with some minor 
additions — do the job. As the cable 
business grew, so did the complex- 
ity of their scrambling methods. 

As I told you when we first started 
out on this trip Into cable video land, 
ripping the video signal apart is 
easy — putting it back together suc- 
cessfully is something else entirely 
The amount of messing up that's 
done to the standard video signal is 
directly proportional to the cost. 
More intense scrambling is more 
expensive. Cable operators have to 
balance their degree of security 
against the cost of the equipment. 
Also, the larger the customer base, 
the less expensive the scrambling 
^ system has to be. In New York City 
(and other large areas), the cabfe 
-| companies have a lot of subscrib- 
g ers. each of whom needs a cable 
- box. The more boxes the cable 
J company has to buy (they don*t 
^ make them themselves), the more 
g money it has to keep tied up in its 
g inventory. 

UJ The old suppressed-sync system 
was a one-way deal. If you got a box 
that could descramble one channel. 



it could descramble any channel 
Which channels would be un- 
scrambled was determined by one 
of the wafers on the channel selec- 
tor dial A position would be either 
jumped or open, which was a major 
caWe company headache for two 
reasons. The first was that they had 
to open the boxes and solder or cut 
traces to configure the box for a 
given customer. The second was 
that some enterprising people real 
ized what was going on. opened up 
their cable boxes, and reconfigured 
it themselves. 

The only way the cable compa- 
nies could guard against that was to 
use screws with oddball shaped 
heads to hold the box together. 
When that didn't work, they started 
using screws that had a left-hand 
thread. But enough history. 

What the cable companies 
needed was a way to talk to each of 
the boxes individually, while they 
were in customer s homes. Making 
such addressable boxes also meant 
that several scrambling methods 
could be used; the boxes could be 
told which method v^^s in use at any 
one time. Since that information 
couid be sent to the box during the 
vertical blanking interval (while the 
beam was off the screen), the cable 
operator could change the scram- 
bfing method from field to field^ — up 
to sixty times a second. The boxes 



could also keep a serial number in 
an EPROM or some other storage 
device, which meant that boxes 
could be addressed individually and 
the descrambling circuitry could be 
turned on and off for separate chan- 
nels from the main cable company 
office. The cable companies loved 
it. 

Understanding that kind of stuff is 
a bit more difficult than the old sup- 
pressed-sync system, but if you 
take the pieces one at a time, it all 
gets cut down to manageable, bite* 
sized chunks. Although the cable 
company's scrambling delivery sys* 
tem became much more sophisti- 
cated, it was still faced with the 
same cost restrictions when it had 
to decide which of the available 
scrambling techniques to use. 

One of the most popular choices 
was the so called SSAVI system. 
That s an acronym for Sync Sup- 
pression Active Video Inversion. It 
allows the video to be delivered to 
your doorstep in one of four flavors: 

• Suppressed horizontal sync and 
normal video (Fig. 1). 

• Suppressed horizontal sync and 
inverted video CFig. 2). 

• Norma! sync and suppressed vid- 
eo (Fig. 3X 

• Normal sync and normal video 
(we can forget this one). 

Before we get into the nitty gritty 
of the SSAVI system, there are a 




RG< 1— THE SSAVI SYSTEM can deliver video with suppressed horizontal sync and 
nomiet video. 



\^ — coNmot: 




FIG. 2— SUPPRESSED HORIZONTAL SYr^C and inverted video is also possible with 
the SSAVI system. 



This isn't as strange as it might 
seem. In a normal video signal the 
reference for color is the burst sig- 
nal that follows horizontal sync- The 
colorburst signal lasts only a bit lon- 
ger than 2 microseconds, but it s 
used as a reference for the whole 
video line, which is about 63 micro- 
seconds long. As far as color cor* 
rection is concerned, that means 
there's no real reference signal avail- 
able for more than 95% of the line! 
The cobr phase for the rest of the 



few basic things you shoufd know, 
because they tell you some interest* 
ing things about how the system 
works. 

The first is that horizontal sync is 
never inverted — even rf the picture 
is rnverted. This means that any cir- 
cuit designed to descramble it has 
to separate the two basic parts of 
the video line (control and picture 
firsti We have to be able to turn the 
picture right side up Cif needed) 
without inverting the control section 
as welL 

The SSAVI system seems even 
more complex when you realize that 
the job of separating control and 
picture has to be done on lines that 
might very well have no horizontal 
sync pulse that can be used as a 
reference mark. In the older sup* 
pressed-sync system, the sync 
could be recovered from the gating 
signal that was buried in the audio: 
with the SSAVI system, there s 
nothing like that available. 

The key to regenerating the video 
signal is based on the fact that all 
aspects of tt are tied together in a 
strict mathematical relationship. If 
you can locate one part of the sig- 
nal, you can determine where every- 
thing else has to be. 

The broad picture for a de- 
scrambler, therefore, is to design a 
circuit that can identify one part of 
the signal, and then use the repeti- 
tion of that signal as a reference for 
restoring the rest of the video. You 
should realize by now that weVe 
talking about a phase-locked loop, 
or PLL. Even if the identifiable com- 
ponent of the video occurs only 
once a field Cor even once a frameX 
that's still often enough to control 
the frequency of a voltage*con- 
trolled oscillator, or VCO, and lock 
the PLL to the received video. 



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FIG. 3— HERE'S WHAT NORMAL SYNC and suppressed video look like. 



line is based on the stand-alone 
3. 58- MHz generator that's a normal 
part of the TV set. 

Building a SSAVI descrannbler 
isn't as easy as building one to fake 
care of suppressed sync, but it's not 
as difficult as you nnight think. Be- 
fore we start to work out the details 
of the circuitry, we have to draw up a 
comprehensive list of exactly what 
we want the circuit to do. A circuit 
designed to descramble the SSAVI 
system needs the following basic 
features: 

• A means of knowing if the picture 
will be normal or inverted. 

• The ability to generate horizontal 
sync pulses. 

• A way to rdentify a definite point 
in the received video, 

• A circuit to place horizontal sync 
pulses at the right point 

Some SSAVI systems also play 
games with the audio, but the meth- 
ods used to hide the audio have 
been around for a long time. The 
audio is usually buried on a subcar- 
rier that's related, in some mathe- 
matical way to the IF component of 
the TV signal. We'll get into that 
briefly when we take cane of restor- 
ing the picture. 

Although we'll be working out the 
details of the circuitry next time, you 
should already have some ideas of 
what it has to be like. The SSAVI 
system uses digital signals for se- 
curity and access rights— the stuff 
that cable executives lie awake all 
night thinking about (instead of less- 
important things such as impruving 
picture quality, increasing channel 
services* and v^dening the audio 
bandwidth. Because the first step in 
handling SSAVI scrambled signals 
is to locate a known point in the 
signal, we'll be using counters and 
other standard digital logic to keep 
track of where everything is sup- 



posed to be. Thafs right people, 
most of the guts of a SSAVI de- 
scrambler are made of the same 
standard digital stuff we've been 
using in this column since the begin* 
ning. 

In the hiture we'll lake apart a 
typical frame of SSAVLencoded 
video and see how v^^ can put it 
back together again correctly Its 
not as complicated as you think and, 
to tell you the truth. I wouldn't be a 
bit surprised if a bunch of you read- 
ers beat me to it In the meantime, 
to help you appreciate what's in- 
volved in scrambling a video signal 
next month we'll work on some cir- 
cuitry that will scramble a perfectly 
good video signal. R-E 



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COMPUTER CONNECTIONS 



I 

Miniature multimedia machines. I 



JEFF HOLTZMAN 



Apple has indeed announced 
a second miniature multi- 
media machine CMMM). as 
rumored here fast month Newlon, 
the first MMM. will be designed and 
produced in conjunclron with Sharp 
Electronics, and is more computer 
than gadget. Sweet Pea. the sec- 
ond, will be designed and produced 
in conjunction with Toshiba, and is 
more gadget than computer. 
Whereas Apple has publicly shown 
the hand -wired Newton prototype. 
Sweet Pea appears to exist only at 
the conceptual level. Nonetheless, 
the implications and technology be- 
hind Sweet Pea are enormous. 

Newton has no keyboard, but 
uses a stylus for input, Connectrvity 
to other Newtons. and to PC s and 
Macs, is also strong. The point is to 
service students, executives, facto- 
ry workers, and others who need 
on-the-go computing that inte- 
grates smoothly and cleanly with 
desktop systems and networks. 

Sweet Pea. on the other hand* 
appears to be aimed squanefy at the 
consumer market, in particular, a 
segment that some are calling by 
the awkward term infotainment, 
which attempts to combine learning 
and entertainment. Sweet Pea will 
play specially prepared CD's con- 
taining text, graphics, audio, and 
video. According to one Toshiba of- 
ficial, it nf>ay connect to a TV set for 
home use* or it may be portable. It 
should hit the shelves in summer of 
1993. and should be priced under 
Si 000. 

The software technologies be- 
hind Sweet Pea are mighty interest- 
ing. Kaleida. the jOint venture in 
multimedia between IBM and Ap- 
ple, will supply these technologies. 
One is called Script X: it is an author- 
ing language that developers can 
use to create multimedia titles that 
will run on multiple platforms, includ- 
ing Intel and Motorola CPU s. and 



RISC devices. It will also run on spe- 
cial operating systems used by 
MMM's, In fact. Kaleida is develop- 
ing one such operating system, the 
Consumer Operating System 
(COS) that will, of course, support 
Script X. Script X is also slated to 
support Apple s multimedia stan- 
dard, QuickTime. 

Apple has signed deals with 
Warner New Media and Paramount 
Communications to supply titles; 
Claris. Apple's software subsidiary, 
will also develop new titles. 

Kaleida got off to a slow start, and 
has been partially eclipsed by other 
more immediately apparent benefits 
of the historic 1991 accords be* 
tween IBM and Apple. However, the 
fBCenl appointment of a board of 
directors, along with Nat Goldhaber 
as head of Kaleida. not to mention 
the Sweet Pea technology an- 
nouncements. all indicate that Ka- 
leida is likely to be the vortex of 
some fascinating and industry-shab 
irvg new developments. 

Less technologically advanced, 
but likely to have some market im- 
pact, are new pen-based pocket or- 
ganizers that will be introduced by 
Sharp and a joint effort between 
Tandy and Casio. At an estimated 
$300. the Tandy/Casio unit aims to 
undercut initial pricing on Newton 
and Sweet Pea devices. The Tandy/ 
Casio will use the GeoWorks graph- 
ical environment, will have built-in 
handwriting recognition, and will 
have a PCMCIA slot for memory 
and telecommunications. Look for it 
sometime in 1993. The Sharp unit 
adds pen input to the Wizard line, 
and includes an extensive pushbut- 
ton/menu-based interface. Pricing 
was unclear as of press time; the 
device is scheduled for release this 
year Also scheduled from Sharp is 
an 8088-based palmtop that should 
sell for about $1000. 

Microsoft is hankering after this 



market as well. Lately there has 
been discussion about a CD-ROM 
based machine that would run a 
ROM-based subset of Windows, 
connect to a TV set. and provide 
infotainment. Apparentty designed 
to compete in the video- game mar- 
ket, the device is currently going by 
the name Wintendo. 

Upheaval in the PC business 

In the beginning was the PC. 
which meant an 8088 and one or 
two 360K floppies. Then came the 
XT, which added a hard disk and 
bumped memory up to 640K Next 
came the AT which added a full 16- 
bit pnocessor and peripheral inter- 
face. Then came the 386. which 
brought 32-bit processing and un- 
heard-of performance. For a good 
four or frve years, the boundanes 
between those four divisions were 
clear However, in the past two 
years, the introduction of new 
CPU's by both Intel and its rivals has 
almost completely obliterated 
those bounds. Now there is a 
smooth spectrum of often overlap- 
ping price/performance choices 
ranging from lowly 386SX's to 50- 
MHz 80486DX"s. It's nearly impos- 
sible to keep in mind all the varia- 
tions among CPUs, including 
speed, bus width, power manage- 
ment. cache size, math 
coprocessor, and system support 
components. Choosing a complete 
system is no longer a choice among 
four well-defined categories. § 

Against that backdrop, manufec- % 
tuners find it difficult to make their 
offerings stand out. In the past year g 
intense price wars have forced sys- ^ 
tem costs to absurdly low levels. At ^ 
first, the price wars were conducted g 
almost exclusively among clone | 
manufacturers, but Compaq re- ^ 
cently joined the fray. IBM has | 
promised to do so by this fall, and 
second-tier suppliers like Dell have gi 



already retaliated. One industry 
analyst has stated that there are 
some 500 PC suppliers, of which 
450 shouldn't exist. Another ana- 
lyst suggests that within a few 
years, the vendor base will be re- 
duced to a dozen multinational cor- 
porations that supply 95% of 
industry needs. 

Another trend is that toward in- 
creasingly dense integration, both 
at the chip and the system level. For 
examplen the original PC used 16K 
DRAM s. Todays standard is 4 
megabits, an increase of 256 times. 
Back then, system logic was built 
from hundreds of discrete TTL com- 
ponents. Today, three or four VLSI 
IC s do the same job. At the system 
level many motherboards today 
contain built-in serial and parallel 
ports, hard- and floppy-disk contnol- 
lers, and expansive memory — 16 
megabytes or more. By contrast, 
original IBM motherboards seldom 
held more than 51 2K of memory, 
and contained nothing but the re- 
quired system logic. 

Together, price wars and the 
larger trend of increasing integration 
lead to the necessity of product dif- 
ferentiation, or some means of mak- 
ing your product stand out in the 
customers mind from that of your 
competitor. Price cutting is one wgy, 
but It can only go so far. The other 



way is to add features, and that s 
what well start seeing this fall. 

Look for systems with built-in net- 
working and sound capabilities. 
Look for systems from IBM and 
others with preinstalled operating 
system software COS/2. DOS/Win 
dowsX Look for systems with tons 
of bundled applications. Look for 
creative marketing schemes, (For 
example. DAK. a mail-order house, 
now gjves away a 386DX/33 with 
purchase of $1500 worth of soft- 
ware — and quality stuff at that, in- 
cluding current versions of Win- 
dows, Word for Windows. Norton 
Desktop. Adobe Type Manager. Par- 
adox, and more). Look for pre- 
assembled networks supporting 
anywhere from 2 to 250 users. Look 
for hard-drive upgrades from Sea- 
gale and others with preinstalled 
software (Windows). Look for laser- 
printer upgrades that incfude RAM 
with font and emulation cartridges. 
Look for operating systems (Win- 
dows and 0S/2> to include more 
and more features traditionally as- 
sumed to be part of the applications 
realm, e.g.. networking and E-mail 

The following are several trends 
to watch: 

CPU Wars 

Intel continues to try to fend off 
attacks on its 386 business— AMD 



expects to take 50% of the market 
by the end of this year — but both 
AMD and Cyrix are mounting new 
offensives on the 486, Cyrix will in- 
troduce 25-, 33', and 40-MH2 ver- 
sions of its 486 clone at about half 
the price Intel charges. Meanwhile. 
AMD plans similar introductions^ 
but a recent legal setback could 
stall its efforts. IIT is also entering 
the race: the company stated re- 
cently that it is developing a 486 
clone with integrated video display 
and image compression hardware, 
paralleling Intel's efforts to combine 
an X86 CPU with IBM s XGA graph- 
ics and Intel's own Digital Video In- 
teractive (DVD, a digital system for 
compressing and playing back vid- 
eo on standard PC's. Timely intro- 
duction of the latter could be the 
breakthrough PC-based multimedia 
has been wailmg for 

Intels P5 (sometimes known as 
the 586. although reports indicate 
that Intel is searching for a new 
name) contains two CPU s. a 486- 
compatible unit, and a Reduced In- 
struction Set Computing (RISC) 
unit. V#iat's the value of sticking a 
RISC chip in a PC? On the other 
hand, what would be the value of 
sticking a 486 in a workstation (nor- 
mally powered by a RISC chip)? In a 
PC. let the 486 do PC things (DOS. 
Windows. OS/2), and let the RISC 
unit run the \ndeo system or a dedi- 
cated compressron/decompres' 
sion unit. In a v/orkstation. let the 
RISC unit do Unix things, and let the 
486 provide PC compatibility. 

Power Play 

Power consumption is becoming 
a hot topic not only among note* 
book PC vendors, but among desk- 
top system vendors as welL 
Consumers demand longer battery 
life fnom their notebooks — a mini- 
mum of eight or ten hours. Desktop 
vendors need to cut power con- 
sumption for reasons of energy con- 
servation. Significantly reducing 
energy consumption by computers 
would save $1 billion per year plus 
reduce CO^ emissions by the equiv- 
alent of 5 million automobiles during 
the same period. Achieving these 
reductions is not wishful thinking; a 
recently formed industry/govern- 
ment coalition that mcludes the 
EPA. Apple. Compaq, DEC. HR 



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IBM, NCR. Zenith, and otfier man* 
ufacturers announced a set of de- 
sign parameters centered around 
several types of "sleep" modes and 
3.3-vDlt system components. The 
goal Is to reduce power consump- 
tion of the average PC to 30 watts. 

AMD is pnomoting 3-volt system 
design guidelines, and it says that a 
complete PC chip set will be avail- 
able this summer with product in- 
troductions (probably centered 
around notebooks) scheduled for 
fall COMDEX. To support this bur- 
geoning nnarket. Intel has an* 
nounced a 3. 3-volt version of the 
386SL that includes a fully static 
CPU, cache controller, bus and 
memory controllers, that can inter- 
face with both 3.3- and 5-voit pe- 
npherals. Cirrus Logic has intro- 
duced 3 dual-voltage video control- 
ler. 

Just Add Water 

Networking is not yet hilly per- 
vasive. However, new chip designs 
promise low-cost system additions 
that will further spread the ability to 
link up. One study shows steady 
growth in units shipped per year dur- 
ing the period 1989 (2.2 million) 
through 1995 C6.7 million). AMD has 
introduced a single-IC Ethernet 
adapter that (along with simitar de- 
vices from National, SMC, and 



others) is going to further increase 
the availability and use of networks. 
The chip will be a built-in component 
on many new motherboards: sev- 
eral influential PC systems houses 
(Apple, Compaq. Delt HR North- 
gate) have already introduced (or 
will shortly) systems with built-in 
network adapters. Couple that with 
increasingly aggresstve marketing 
by Novell plus built-in network c:a* 
pabilities of the next version of Wrn- 
dows — and you've got instant 
networking. 

The Magic Bus 

Windows and OS/2 demand fast, 
high-performance computers. As 
clock speed increases, getting data 
in and out of the CPU becomes 
more critical to maximizing system 
performance. Our trusty old system 
buses (ISA, EISA. MCA) simply 
amn't up to the task. In recent 
months, computer manufacturers 
have added a local bus that provides 
a direct path between the CPU and 
some other component, usually a 
special video adapter. So fan how- 
ever, these efforts have been ham- 
pered by a lack of standards. 

In response. Intel and an industry 
consortium called the Video Elec- 
tronics Standards Association 
(VESA) have each devised its own 
local bus standard (see Fig. 1). 



Some published reports have 
claimed that the two standards will 
compete with each other; however, 
Intel officials have stated publicly 
that the two efforts are complemen- 
tary. Both share throughputs in the 
120-130 megabyteS'per-second 
range. The VESA spec includes a 
connector design (based on a Micro 
Channel bus connector) that the In- 
tel spec currently lacks. On the 
other hand, the Intel spec includes a 
special interface IC that helps iso- 
late the CPU from I/O sub- 
systems — and that presumably 
allows for transparent CPU up- 
grades via the company's Over- 
Drive technology Due to bus-timing 
and signal-reflection issues, local 
bus slots v^ll most likely be limited 
to thiBe, e.g., one each for video, 
network, and hard-disk control; the 
latter could be a SCSI host adapter 
for connecting multiple devices. The 
regular expansion bus would then § 
be limited to slow-speed devices. 

In short, the next few years v^ll 
see many PC vendors dropping out: S 
the ones that remain will be fighting 
tooth and nail to establish their ^ 
products with increasingly dense in- s 
legration of hardwans and software 
components. Price wars are already _ 
raging: feature wars are just about i 
to break out. This is going to be one 
heck of an interesting battle. R-E 93 



HAND! TALKIE 

continued jrom page 60 



ed, variable Polyswitch resistor 
R30 could Irip and/or the out- 
put power MOSFET's could 
overheat. 

When using the flexible "rub- 
ber ducky'Vantenna* it might be 
necessary to fine tune capacitor 
C30. taking care to keep the an* 
tenna away from people or large 
metal objects. 

After tuning the transmitter 
set up the receiver. TUrn the 
power ON and set the squelch 
control fully counterclockwise 
(off). With the 32-ohm speaker 
connected, increase the volume 
until the background noise is 
audible. Using the oscillocope. 
look at the output from 
REcowRKD AUDIO piu 16 of the 
FM receiver chip IC3, and adjust 
inductor LIO so that the signal 
reaches a maximum level. 

If an FM-modulated RF source 
is avaliable. connect it to the an- 
tenna jack and set it to a 1 mi- 
crovolt output level. Set the 
audio signal to 1 kHz and the 
deviation to 4 kHz. Adjust LIO 
for a symetric waveform on pin 
16 of iC3. The tone should be 
audible in the speaker. Set the 
input level toO.3 microvolts and 
adjust L3 for minimum noise 
level. (This adjustment is op- 
tionaJJ 

The range of the transceiver 
with the specified antenna is 
one to three miles» depending 
on background noise and the 
proximity of buildings or geo- 
graphical obstructions. The 
range can be increased with a 
citizen band (CB) base station 
antenna, or if its transmission 
frequency is set for the 10-meter 
amateur radio band and a suit- 
able antenna for that frequency 
range is connected. 

To change the transceivers 
frequency from 25 MHz to 31 
MHz* change crystals 1 and 3 
(XTALl and XTAL3) and tune 
the transceiver according to the 
instructions given earlier {See 
the Parts List for the crystal 
specs,) To operate the trans- 
ceiver outside of the 25-MHz to 
31*MH2 bands, the transmit fil- 
ter as well as the multiplier com- 
ponents must be changed. R-E 



VERSAiriE OSCILLATOR 

continued from pugc 74 



That resistance value will keep 
the peak speaker currents with- 
in the 200-milliampere output 
limit of the 555, The output 
power of this alarm circuit de- 
pends on speaker impedance 
and supply voltage, but it can be 
as high as 750 milliwatts with a 
75-ohm speaker and a l5-voIt 
supply. Notice that C3 ia an elec- 
trolytic capacitor 

Figure 19 shows how the out- 
put power of the circuit In Fig, 
18 can be boosted to several 
watts with buffer transistor Ql, 
The resulting high speaker out- 
put current can introduce a sig- 
nificant ripple voltage to the 
power source. Diode 131 and 
electrolytic capacitor C3 protect 
the 555 from the effects of that 
ripple. Diodes D2 and D3 clamp 
the inductive switching spikes 
from the speaker and protect Ql 
against damage. The circuits in 
Figs. 20 to 23 have a similar 
output stages, 

Figure 20 shows how a pair of 
555 s organized as as I able mul- 
tivibralors lorm an 800-Hz 
pulsed-tone alarm generator In 
this circuit ICl is wired as a 
500*H2 alarm generator, and 
IC2 is wired as a 1-Hz oscillator 
that triggers ICl on and off 
through diode Dl once per sec* 
ond, thus generating the pulse- 
tone alarm. 

The circuit In Fig. 21 gener- 
ates the penetrating two-tone 
**he-haw*' sound of Ein^opean 
emergency vehicles. Here, ICl is 
also wired as an alarm gener- 
ator and IC2 is wired as a I -Hz 
oscillator. But In this ease the 
output of IC2 frequency modu- 
lates ICl through resistor R5, 
The output frequency of ICl al- 
ternates symmetrically between 
500 Hz and 440 Hz in one-sec- 
ond alternating cycles. 

Figure 22 shows a circuit that 
generates the wailing noise of a 
police siren. Here IC2 is wired as 
a low- frequency oscillator with a 
cycle period of about 6 seconds. 
The slowly varying rnmp wave- 
form of IC2, buffered by emitter 
follower transistor QL frequen- 
cy modulates alarm generator 
101 through resistor R6, In this 



circuit ICl has a natural center 
frequency of about 500 Hz. The 
alarm output signal starts at a 
low^ f requeue); rises for three 
seconds to a high frequency, 
then decays over a period of 
three seconds to a low-frequen- 
cy before repeating itself as long 
as power is applied. 

Finally the circuit in Fig. 23 
generates an alarm that simu- 
lates the "Red Alert" that is often 
heard in the Star Trek TV series. 
The sound starts at a low fre- 
quency and rises to a high fre- 
quency in about 1.15 seconds, 
ceases for about 0.35 seconds, 
and then starts rising again 
from a low frequency. Here 
again, the sound pattern re- 
peats as long as power is applied 
to the circuit. 

The 555 labeled 1C2 is wired 
as a non-symmetrical oscillator. 
Capacitor CI alternately 
charges through Rl and diode 
01, and discharges through R2. 
The result is a rapidly rising and 
slowly falling "sawtooth" wave- 
form across CI. After buffering 
by Ql. this waveform frequency 
modulates pin 5 of ICl through 
R7. causing the output frequen- 
cy of ICl to rise slowly during 
the decay part of the sawtooth 
waveform and to collapse 
rapidly during the rising part of 
the sawtooth waveform. 

The rectangular waveform at 
pin 3 of 1C2 turns ICl off 
through common-emitter am- 
plifier Q2 during the decay 
phase of the alarm. Therefore, 
only the rising parts of the 
sound pattern are heard which 
sound very much like the Star 
Ti-ek Red Alert, 

The ou tpu ts of most of t he cir- 
cuits in this article have been 
taken from output pin 3, but 
many of the figures haven 
shown triangular waveforms 
developed across the timing ca- 
pacitor (e.g. Figs, 3b, lib, 13b 
and 15b)* There might be occa- 
sions when you will find those 
sawtooth (or ramp) waves 
useful. You can obtain a saw- 
tooth by tapping the charge 
voltage across the timing capac- 
itor. By charging the capacitor 
with a constant-current source 
instead of a simple resistance, 
the ramp can be made quite lin- 
ear. R-E 



Countersurveillance 



Never before has so much 
professionaf information on the art 
of detecting and eliminating 
electronic snooping devices — and 
how to defend against experienced 
information thieves— been placed 
in one VHS video. If you are a 
Fortune 500 CEO, an executive in 
any hi-tech industry or a novice 
seefiing entry into an honorable, 
rewarding field of work in 
countersurveiilance, you must 
view this video presentation again 
and again. 

Wake You may be che vicrim of 
stokn words — jsrtctous ideas that ^^wld 
have made you vtr>' wtrakhy! Ycs» profcs- 
sionaJs, tntn rank amateurs, may be lis- 
tening to your most private con- 
versations. 

Waktt iipf If you att.- not the victim, 
then you ate surroundt'cl by cuurttless vic- 
tims who need your help if you know how 
to discover telcpho tiu caps, locate bugs* or 
"sweep** a foom clean- 

There is a thriving professional service 
steeped in hi^h-tech techniques that you 
can become a part oil But hrst, you must 
know anil understand Countfrsurveihince 
Technology. Your very first insight into 
this highly rewrdin^; field is made possi* 
ble by a video VHS prcsentarion that you 
cannot view on broadcast television, sat- 
ellite, or cable. It presents an informative 
pmgram prepared by pnjtessionals in the 
field who know their industry, its tech- 
niques, ktnks and loopholes. Men who 
can tell you more in 4") minutes in a 
straightfor\^'ard, exclusive talk than was 
ever attempted befoR\ 

Foiling Information Thieves 
Discover the targets professional 
snoopers seek out! llic prey irc stock 
brokers, arbirrti^e hrms, mnnufacturt.TS, 
high-tech companies, any competiiive 
industry, or even smalt businnesscs in the 
same community. Tlie valuable informa^ 
rion they filch may be marketing strat- 
egies, customer lists, protluct formulas, 
manufacturing techniques, even adver* 
rising plans^ Informarion thieves eaves- 
drop on court decisions, bidding 
informarion, financial data. Tiie list is 
unlimited in the mind of man— <*s- 
pecially if he is a thieH 

You know that the Russiatis secretly 
installed countless micmphones in the 
concrete work of the American Embassy 
building in Moscow. TTicy converted 




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w^hat Wp-as to be an embassy and pri^-atc 
residence into the most sophtsticated tv* 
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down in order to a- move all the bugs. 

Stolen Information 
Tlie opt^n taps fmm where the informa- 
tion |H»urs out may be fn>m FAXs, com* 
puter communications, telephone calls, 
and everyday business meetings and 
lunchti me encounters. Businessmen need 
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someouir may he listening ut recording 
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meaningful information. 



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PItiH' ni>h m\ oipy itl iht' C iniiiHT^nri fill j rut' Tc-vliii^Ujm'!^ 
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The professional discussions seen on 
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communications. In fact, do you know 
how to kmk for a bug, w-here to look for a 
bug, and what to do w^hen you find it? 

Bugs of a vvry small size are easj' to 
build and they can be placed quickly in a 
matter of seconds* in any objecr or room. 
Today you may have used a telephone 
handset rhar was bugged. It probably 
con tat fled three bugs. One was a phony 
bug to fool you into believing you found a 
bug and secured the telephone, Tlie sec- 
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The professional is not without his 
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Some of this equipment can be operated 
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The pmfessiormls viewed on your tele- 
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This advertisement was not written by 
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To obtain the information contained in 
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Inc., P.O. ioi 240, Massapequa Parlt. NY 
11762-0240. 



AUDIO UPDATE 

continued from page 78 



sical-music audience and the poor 
audio quality of most FM broad- 
casts. In any case, the question re- 
mains: Is the listening public really 
interested in AM stereo? 

I don*t relish raining on anyone's 
parade, but I suspect that (to mU a 
metaphor) the AM-stereo band- 
wagon will never get off the ground. 

Consumer f raod? 

One of the panel discussions at 
last falls Audio Engineering Society 
convention was titled "New Cabfe 
Designs: Innovation or Consumer 
Fraud?" The organizer of the event 
was strongly anti-cable and had 
stacked the panel accordingly One 
^ of the surprising guests was 
^ Witfnedo Lopez, a non-audio person 

I fn^m the New York City Departnnent 
^ of Consumer Affairs. He presented 

. his departments view about what 
J constituted fraudulent advertising, 
g and suggested that most audio 
c components are "blind" items, 
^ meaning that the average consumer 

II is not in a position to judge the valid- 
ity of advertising claims. Deceptive 

96 practices include "false implica- 




The AMAX logo will Identny AM re- 
ceivers that meet Itie NRSC require- 
ments. 



tions of quality or characteristics of 
the item." Mr Lopez went on to say 
that if his agency finds stores trying 
to sell a speaker cable that is heav* 
ier but not better— but they are nev- 
ertheless claiming it is— it might 
take action against them. 

I would caution Mr. Lopez to tnead 
carefully, in any area where consum- 
ers are being sold "dreams" — prod- 
ucts that purport to make them 
slimmer younger more beautiful or 
their equipment better-sounding — 
they don^t want to be told that they 
are being deluded. For example, the 
cosmetic industry would seem ripe 
for such an investigation with its eel- 
lulite removal creams, skin re- 
juvenators and other such products. 
Is it a defense or justification for the 
manufacturer to say that the con- 
sumer "thinks" the product works, 
notwithstanding objective evidence 
to the contrary? 

In truth, it had never occurred to 
me that the absurd claims made by 



many high-end cable and accessory 
manufacturBrs could be legally de- 
fined as fraudulent. In the years that 
Tve been dealing with audio equip- 
ment claims, I never became very 
upset by the sometimes technically 
off-the-^wall— or at least unpnoven — 
pronouncements of the various 
manufacturers. As a matter of fact, t 
even had a hand in writing some ads 
and technical papers for various 
companies promulgating their 
sometimes strange technological 
points of view. 

Because the literature was aimed 
at a high-end audience, I felt no guilt 
at piwidtng the kind of nonsense 
they loved to hear After all, I ra- 
tionalized, it wasn't as though the 
outrageously priced equipment was 
depriving anyone's wife and children 
of food. 

My ultimate conscience-clearing 
maneuver was to editorialize under 
my own name against some of the 
properties (ultra-wide bandwidth, 
olefin cable insulation, dual-power 
supplies, etc.) that I had extolled in 
the ads. In any case, I took (and still 
take) none of this very seriously- 
and I regarded my jabs and jibes at 
audiophile nonsense as editorially 
interesting but not really powerful 
blows for truth, justice, and the 
American Way. R-E 



BUYER'S MART 



FOR SALE 



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PLEASE INDICATE m which category of classrtied advertisfng you wish your ad to appear. For 

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charges for special ads. Minimum: 15 worils. 



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W&accopt MasterC^d and Visa for payment ol Orders. If you wish lo u&o yourcfedil card to pay for your ad ftti 
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RESTRICTED t&cfinical information: Electronic 
surveillance, schematics. locksmtthir>g. cover! 
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SECIIET cable descramblets! Build your own 
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rold. Zentth. Tocom. S.A., eKam^>le Star com -6 
with ^ume 5189,00. Quantity poces aivasiable 
CO O. ofders OfC Fr»e c^aJog. ULTIMATE CA* 
BLE PRODUCTS, (702) 646-6952. 



l\3 



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MARK V CUanONICS, INC. 



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a-iwmiBiiniiiigPftiiwMtff ttfw ifwusrw 

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MARK V KLHCI kONIOi. INC 

ORDER IN CAUFORNIA 1'B0D-52l^MARK 
ORDER OUTSIDE CA l'eOO'4Z3*FIVE 
CATALOG & IMFORMATIOH U13} 8a8'fl988 
OHDER BY FAX (213) 6aa*68&e O 



ClflCLE 93 OH FUEE INFOnUATKW CARD 



CB RADIO OWNERS! 



We specialise rn a wide variely of technical 
^nfomiation, parts and services for CB radios. 
10- Meter and FM conversion kits, repair books, 
plans, fiigh-peiformance accessories Thotisands 
of satisfied cusiomefS since 1976 f Catalog $2. 



CSC INTERNATIONAL 

P,0, BOX 3I500RE. PHOENIX. AZ 85046 



PflOi tui yourseW and aquipfneni from electncal 
shocks. Compfeie unir 398.95. SAFETY-UN- 
LIMITED, 1743 Baldwin Road, Yofklown. MY 
10598. S-HS5 00. 

CABLE equipment at wtiotesate pnoas. Tocom. 
Oak, Zenitti, Jerrotd. SA. Hamlm. ad<f on 6e- 
scramblers. test chips, all fuEly guaranteed. 
S.A-C. 1 {600) 622-3799. M-F 7A-3F PST 

TV conv/descrambler specals DPV Si 89. 00. 
RTC'56 S99.00. Tocom-VIP S250.00. S A. 85XX 
senes S169.00. Zenith Si 99 00. HamEsn 6600-3^1 
S79.tK). full w^antf, MOUNT HOOD ELEC- 
TROKJC^ 1206) 260-0107. 

PCB; printed ctrcurt boai6 art wortt made fo yow 
Specifications plotted on transpafency. Mulii layof 
£rid surface compooeni capable Circuit board 
DfocSuctioo avaiiabte, free estimate send sche- 
matic lo KEGRON ENGINEERING. 159 Gar^ 
Place, BiOdidyn. r^Y 11215 fax i7T8) 766-^028. 

PUVTED thru hole pnmed oxurts S25.00 mni' 
mum Fast turnaround. For more inlorrnattgn call 
KP. CIRCUrrS, (403) 250-3406 or BBS (403) 
^1-9342 (fi n.lj 



WIRELESS CABLE RECEtraS 1.9 TO 2 7 GHl 






i .. . .-iri/ SI 7 J 90 
















i 


smm«mmwen.m^ itiatiiiFM 






n m i mum m twi 

























CABLE Stealth: prolect yourself from de« 
saambrer deled ion and slop the 'tKillet." PreseV 
tested, only S24.99. $4.00 S&H. BALDWIN 
ELECTRONICS, Bq% 929t Baltimore, MO 
21222-0291. 

LASERS, [ight shows, plans, books, .5mw to 20 
watts. Iree calaEog call 1 (EDO) 356-7714 or whie 
MWK INO., 198 Lewis Ct.. Corona, OA 91720. 

IS it true... Jeeps for S44.00 Ihrougl^ Ihe U,S, 
gov't? Toll free 1 (800) 467-8585 or (504) 
649-5745 ext. S-5192. 

JERROLO Impulse digital converter Upgrade 
your 400 450 unit to Inis latest system. (212) 
896<8B19. 



ANTIQUE RADIO CLASSIFIED 
Free Sample! 

Antique Radio's -—j 
Largest Circulation Monthly. [Pf 
ArticCes, Ads S CEa^iiieds. 
6-Monih Trial: SIS. 1-Yr: S27 ($40-1 St Class). 
A.R.C,» P.O. Bosf 802<L9, CariJsle, MA 01741 




THE besi multiplex stereo FM transmttter on Ihe 
marttet, use any audio source and enjOy crystal 
dear FM reception Irom any receivef in your home 
or yard. The JC2010 kit 3s pre tested and only 
requifss your firtal assembfy. 599,95 plus $2.50 
S^H check or mofiey order. No C 00s J CB INC., 
7239 Valley St. Dalton Gardens. ID 83814 (208) 
772-9207. 

GENERAL Instrument DPV-T-s S250.00. Soen^ 
tJfic Altania BSCOs Si 50. 00. Tocom^ Si 50.00 to 
$250.00. CABLE WORLD, 1 (600) 234*7193, 



TEST equipment pre- owned now at affordable 
prices. Signal generators from $50,00. os- 
ciiioscopos from S50.00. Other equipment includ- 
ing manuals avaiiabCe, Send S2.00 U.S. for 
catalog refunded on first order J,B* ELEC- 
TRONICS. 3446 Dempster. Skokie. IL 60076. 
f708)9B2-1973. 

CABLE TV converters* Jerrold, Zenith, Pioneer, 
Oak, Scjentilic Atlanta, and many more. 12 years 
eJtperience gcves us the advantage. Visa MC 
Amex COD ADVANTAGE ELECTRONICS, IHC, 
1 (800) 952-3916 1125 R verwood Dr.. SumsvilEe. 
MN 55337. 



QR£AT Pmject. ZiktU Sin 

gel SSTSft(^S^Re^ 
mindef) taxys 3 HCOtuls 
after 15 seconds Cyde re- 
peats unti okM. ItaoHnnlii, «afaled wtir) braiung 
Cofnpact Ul mmts atop iasftee ts^, PC8, 
mihc, mimictiofts tts PPO 1125: ^"533. V^MC Fr» 
bntchui^ 1 W-39S-56a6 Pr^ m S2a FfD 1$45 
Um. UZJ toil Ot, CrtMbttt. m *321T. 



PLANS AND KPTS 



FASCINATING electronic devices? DazersI 
Lasers' Transmittefs! [detectors! Free energy J 
Tesia' Ktts assembled! Caiasog S4.00 (refunda- 
ble) QUANTUM RESEARCH, 17919*77 Ave., 
Edmonton, AB T5T 2St. 

HO B B Y . bioa d cas t i ng HA M C B surve i I la nee 
transmrtters, amptifieTS. able TV, sdence. boos. 
OCher great prDjects! Catalog Sl^OO. RAHAJOSf 
BoJt 130- Ftp, Paradtse. CA 95967. 

DESCRAMBLERkits. Complete cable kit S44.95. 
Complete satallcte kit $49.95. Add S5.00 snipping. 
Free brochure. No New York sales. SUMMIT RE 
Bo3E 489. B'Onx. NY 10465 



REMOTE CONTROL REYCHAIN 



Coftiptcti^ »f,mJnf--tJ»n4^nltteT 
irtd +S vdcH F recti V PT 

to toiitla your cjwn botc* ttlanti 




Vlsitcctlnc, 
{510)651-1425 



CO>1 ^hflcKVJm (5f wc 
^^H^VO Add % 3 s^ilpplng 

5 @>S19<95,10@$14,95: 

Box 141 56, Fremont, C*. 94539 
Fax {510) 651-8454 



SURVEILLANCE Iransmitter kits tune from 65 
lo 305 MHz. Mains powered dupfex, telephone, 
room, combination teiophone'nxjm. Catalog with 
Popular Communications, Popular Elec- 
tronics and Radio-Electronics book fevi<?ws of 
""Eleclfonlc Eavesdropping Equipment De- 
sign." S2.00. SHEFFIELD ELECTRONICS, PO 
Box 377785-0, Chicago. IL 60637-7785. 

FREEf Sensational catalog of fan kits. LNS 
TECHNOLOGIES. 20993 Foothiil Blvd.. Suite 
307R. Hayward. CA 94541 1511. 

TEST' Aids for tesltng units in full servlve mode. 
Starcom Vil, S40.00; Siarcom VI, S30.00; Star- 
com DPBB. SSO.OO; Pioneer, clears errof codes 
E2 E3 E4 E5, $75,00; Pioneer cubes, wilt not atter 
internal serial number^ St 75. 00: Tocom VIP 
5503^5607, $25,00: S.A. 8S0O, $25.00. 8550 
S30 00: 8580, S40 00: 657090, SSO.OO: Zenith 
2TAC, S25 00; security tods and renxKes. H.E. 
ENGINEERING, (6T7) 770-3630. 

OESCR AMBLING, new secret manual Buifd 
your own descramblers fof cable and subscrip- 
tion TV, Instructions, schen^atrcs for SSAVI. gated 
sync. Sinewave. (HBO, Cinemax, Shovviime 
LIHR Adult) St2,95. SEOO postage. CABLE* 
TRONtCS, Box 30502a, Bethesda. MO 20824. 

WIRELESS guitar transmission system. Buitd 
your own for $39 95! (kit) RADIOACTIVE 
TRANSMISSIONS 1 (800) 263-9221 &d- 2587, 

ETCH PCB s yourseif, new techruque, no chemt- 
cats, easy, cneap^ full instructiorts, shaiefaiB, 
Sf .00, SASE. NICKNAR Suite 297 CN 1907, Vm, 
m 07719. 



BARS bones Eprom programnier. Plans. MS- 
DOS disk $15.00. Also parts kits, assembfod, 
SERGEANT, 309 W. San Ai^oriio, San Marcos, 
TX 76666. 



BEST BUYS BEST SERVICE _ 



2mU£l PROOF TV TESTED 
WAHT TO BUY; 



SATELLITE TV 




FREE Catalog D«lers Wiactd 

UMiti^vtidoti (407)^31-3220 800-335-2350 



WANTED 



INVENTIONS new pioducts ideas wanted: call 
TLCJ for free i nf or matjor\. inventors newstettef. 1 
(SDO) '168-7200 24 hours^ day - USA Canada. 

INVENTORS: Wo submil idoas to industry, Find 
out what wo can do for you. 1 ^600) 2ea-fDEA. 

FORMAL blueprints from sketches and scratches 
— reasonable — confidential — mech eleo drait- 
lag. MICROCHIP THEATRE (718^ 398-1163- 
Leave message 



INVENTORS 



INVENTORS! Can vdli patent and prEjTil from yogj 
idea? Call AMEIIICAN INVEHTORS CORF^ foi 
free mformatkyL Servifn invefLtors srnce 1975. 1 



SATELLITE TV — E>o i1 youfsell — major brands 
discounted, we' It beat everyone's price. DIS- 
COUNT LARRY {BOB] 596-0656 

V10E0C1PHER \l descfambiin^ manual Sche* 
mat>cs. video, and audio. Estplains DES. Eprom, 
CloneM aster. 3 Musketeer, Pay-per-view |HBO. 
Dnemax, Shov^time. Adult, etc ) Si 6. 95. S2,00 
postage- Scfiernaiics for Vtdeocypher Plus« 
$20.00. SchemMk:s for VideocypFier 032, $15.00. 
Collection of software to copy and alter Eptom 
codes. S25-00. CABLETRONICS, Box 30502R. 
Belhesda. UD 20824. 



CABLE TV 



-800-582-1114: 



FREE CATALOG 

CUUtANTEED BEST PIIICES ' lUMEOlATE SHIPPING 

; .M.K. ELECTRONICS. ^^ 

Pjcnl 0362 Pines Qivd. Suite 3TG vnZ^4 

Pembroke pines. Fl 33024 vSsSSi 



PAY TV AND SATE LUTE DESCflflMSltNO 

AU NEW mi mum ali kew 



Soiintiling Km, ISS? H«r1tl An.. 




Cable TV 



> The Ikrft C«tt|}(e1t Line of DntroiRblerf 
>Frieiidtf, prafeisional lervjct 

>FR£E Cotalog 




Go to th« 5ouN6 

NU-TEK ELECTRONICS 

3250 Hatdi RD 
Cedar Parte TEXAS 7S61 3 



BUSINESS OPPORTUNITIES 

YOUR own radto station! Licensed unlicensed 
Af^, FM. TV. cable. Information St. 00- BROAD* 
CASTING. Box 130-F10. Paradise. CA 95967. 

LET tfie government finance your smati busiriess, 
GfafitsioaJis to SSOO.ODO. FJee reco/ded mes- 
sage: (707) 44&^d600. (K51) 



Is Bad Service Driving You Nuts? 






ELECimracs 




So don't cracli up. Call MCfi 
Electronics, toll free, at 

l'800'543-4330 

or fax l-513-434'6959- 
We'll send you our free catalog. 
And show you how sane excellent service can be. 



Business gets crazy enough without 
your electronic parts supplier driving 
you up the wall* That's why MCM 
Electronics dedicates itself to 
customer service. Well answer and 
service your calls in just thirty 
seconds. We'll also answer your 
questions and give you advice. 
Whatever you need. Then we H use 
our computerized order entry and 
inventory control systems to speed 
your order to you within 24 hours. Of 
course, you get more than quality 
service. You get quality parts and 
components; more than 17.000 of 
them, all available in our huge 
distribution center. 



CAU. TOLL FREE 
1-800-543-4330 



MCM ELECTRONICS 

650 CONGRESS PARK DR. 
CENTERVILLE. OH 45459-4072 



9 




RE-79 



CmCLE B7 OM FREE INFORMATION CARD 



99 



1*800-8314242 Your Resource for 



Test! Measurement and Prototype Equipment 



Jofiieco SeldarloM Braadboartls 




pf IHotaiyping -uid dfcuit tlnifs- mcddi fbnirt i hatf-dti^ jtumioun ludungwrdi tiDto^iod 



fiut No. Frodttci No. 




COBMCI Polfttl 


Blntlijii Poses 


Prkc 


20600 


JE2I 


3,25x2.125 


400 


0 




20712 


JEIJ 






Q 


6J5 


20757 


|04 






2 


12J$ 


20773 


JE2S 






3 




20790 


JE2& 


6J75xl7S 




4 


1495 


20i1l 


JQ7 


7^x7-50 


3J50 


■1 


5Z.fS 



GoldStar lOMHx Dtfcil Tra€« Oscilloscope 




£rw DC 19 20 MKi^ Tift GoUScv iw^Slos^ 

wtd) t«A»40MHi pati0> rim fuiev pm-cf cnrd, Dpctaoon 

Buaiul, icimMtki aad t4oti jjid mm% dG^^. Ii i 

PmMB. faiJiiCtNa. PoqipttW BdCC 

mSSl CS7Q20 OicillaK^ 



Addtfional GoldStar 
Oscilloscopes 



Product 



660SI GS904RD 40Mhi 1 

66077 GSSlOO ItKIMhfJ 

(Mcilkiivopc^a 349.95 

Call for additiomii Goidstar 
test equipment 



J AMECO * 



24 Hour Toil -Free (^rdcr Hodme 



Norionol ond Intel 
^ Dotabooks 




Motox Digital fAuMmotofs 

* .^{ofiLra AOLXI wic^ AO DC curmiE. 
dmdo, uAfimiffir, ind usbumk omnt gvn (except Mif^OO 



M365liacM46SO«ilr: 

* AIkO ixi«4iurci frf«|LKi}Cf and gpiritincc 



17115 MUtOO 

27078 M.I610 

27140 MJ900 

270&6 M3650 

27158 M4650 



J. 5 dtpt rTiuliimctcr»439»9$ 
di^t multinictcT»»f9.fS 
5.5 dipt multimctcf 

with tach/d wcll . 59*95 

3.5 digit niultimctct 
w/ftrtjLirrlcy 

Bt capacitiiricc *Kt»**i*.+i*«74.95 
4.5 digji wt 

liwquciicy 4 a.pjc(tafiee 

at dati halJ >wiiciu^,«99»95 




Mt(i50 




IC Test aip Series 

• Tet dipi tlaigiicd &f tcibpcnij cncuKaKifls |o 0]? 



* Hei^f'ifinf qinnf la»ded Iue^ pniriflD pnimccDiitKt 





rrci6 


1 6-pin 


PflC* 






fix iH&l&fiRlO) 


S5,9S 


22110 


JTC20 


lO-ptn 










^ 6,95 


22146 


fTC24 


24 -pin 


—,....7,95 


22162 




2«pifl 


.,,,.^95 


221S9 


jTC40 


40-fin„„„.„«^^.. 


n « 



EPKOMs - for your prograntRitng noods 



PmNa. P»d«iNdLDtiiJifti«i 







Price 


Pan No 


■ Pf oduci No. 










55566 




402a 


2764A-25 15.49 


65904 


27C25&-I2«^49 


53601 


TMSIS64 - 




59A29 


27C64-15.«™5.95 


59714 


27C256-J5 S.95 


53£ll 


TMS2716«« 


^5.95 


39*45 


27C64 25— 




59722 


27056^ 20«, 




J7647 


I701A « 


^.95 


39«53 


27G&4*45— 




39751 


27C25fr25^ 4.95 


39909 


2?m ^ 


.^4.95 


3W2 


27l2aOTP 2.49 


40184 


2751201T«. 


««4.95 


40002 


2716„«^ . 




59925 


27128-20..«* 


«...7.9S 


40)50 


27512^20 ^. 


.»6.75 


400n 


27lf^ 1 


.«.4.25 


54933 


27128-25 


.....7.75 


40 168 


27512 25. 


.«5.95 


39706 


2n:u\ 


..,.4.25 


59950 


27I2HA-I^ 


4.95 


3?>773 


27C/II2.1].. 


„.7.4S 


400% 


27 


,...4.95 


5996S 


27liaA-20*, 




3*781 


27CSUJ5,. 


..,6.95 


40109 


27>2A iU 


....4,49 


599^4 


2712BA-25,, 


.„J75 


39790 


27C512-20- 


-.,6.49 


40125 


2732Ai5,.... 


...J.49 


59677 


27CI28'15*, 


...,575 


39B02 


27C5l2-25.« 


.,.5.95 


40133 


2732A-*5.«« 


^X95 


59685 


27Cl2i^25« 


«..J.95 


39651 


270010 I5« 


™9.95 


39765 


27C32 


,^4.95 


40O70 


272560T1'.. 


«...4.19 


65699 


270020 1 5«. 


.17.95 


40192 


2764*20™ 




40037 


27256*15...., 


5.49 


65681 


270020-20- 


.15.95 


40205 


2764^25. 




40045 


27256-20 


„„.5.29 


4J692 


68766-35.-- 


»«4.9S 


40130 


2764A20*«« 


--3.75 


40061 


27256-25-^ 


..^4J9 









41224 400026 

41259 400039 

41208 40OOL5 

41504 400101 




Ndtiocul Gcoenl 

PtupoK licetr 

Dnim Dai3i»c]LS]9.95 

Diuk»k_ 19:95 

Au|uliiii^ 

Put poic Lui£^ 
[ Wcf Da£d»(4^ 1 1 .95 
Njtwcul LS/SHTL 
D^ubwilr ,l4.f5 

Djubook 24,95 



41275 


4Q0O44 


392S0 


1J084J 


J9t70 


270645 



A.R.T. EPROM 
Pregrammer 




UVP EPROM Eraser 




27512 OAfr plia the X2fl64 EHFKOM 
* RSl|2|i«>n 

PwffCaL Pfoityrtr^lft. Da cfyioa Prioi: j 15712 

I66S6 EFT PrD9f3nuner_S199.9S ^ 6«o42 



■ DE4 frixi A chip^ otij 21 mimiitD 



DF4 
DEI 



I'«i^Ef»ii^49,9S 



• Partial Listing • Over Electronic and Computer 
Components in Stock! * Call for quantity discounts* 



CIRCLE 114 ON FR£E iHFOBMATtON CARD 



Value. Only a Phone Call Away. 



Compzitei' Upgi^ade Products and Elech'otiic Components 1 



Upgrade your existing tamputer system! Jameco wiU help you upgrade easily and economically. 
1 01 -Kfty Enhanced Keyboonl Mmmmw S03S6SX Motherfaotml 




curKJf ajid numerk ktyt, 

• IBM POXT/AT inJ cttmpitibk cD[ii|>uim 

• Autnmatitilly iwi[chci iKmiccn XT of AT 

• L£D Indkitiin br Nufii^ CipMtid SduU lock hrp^. 



Part No V Pnxtnct Xo. 
67411 KlOl 

Toflilba 1.44MB 3.5>* littoffnfll 
floppFy Disk Driv* 

• IBM rOXT/AT fni ampmbici 
« Giinpii^ Hntiii DOS vawu 3 J oi Ivf^ 

• 72IHCB Amnsiol W (kmicf fnoJe 

• Sor rH * 4*^ » 5.9'D (Ktuil Jirre uaj 



Price 




* Baby moihcrboiid {It.^'il 3*) 

* Irttt 01 one wiji mii vpcnma 

* Su^m up [0 \6MS ^n^M 

* Inrd SOJiTSX/csmpuible miih copracci^ ifidtft 
< AMI BIOS 

* S» ]&liit md rwp S^bii cxpaaiHxi Ixa ikici 
PirtNo. Pf&diKtNo. Description Pfj^ y 



IFif.lf^SN 



JcHii#co IBAA O>iii|Mililil0 Powor S4^ppli#s 




-Edfic 



J£]a34h 

• Ompst -SV 8 -5V * O.SA. 

• 1 50 warn nutp^ pQ^xr 

• S*m*ui>kbCTw«n n<W220V 

• Built- in hn 

■ Onc-)'eir wj.fTiniy 

■ CSA approved 



40774 356Klj Di^k Drive 

Many more upgrade products availahkf 



Part Ho. 



1^5 



PrtJitct No. Dacfiptign 



IIV ^ -t2V t««5A 
■ 200 wans ouipot power 

* Swiich^ bcxwten 1 10/22QV 

* Built^ft &n 

•Sac: 6.rLt5,»»'W)t6"H 

* CSA ippmvcd 



P"« 



JEI056 



1 50 watt PCyXT puwcr iupply.»«..».....$69.95 
2CKJ wa« AT power siippl}r.^,»..t.«.,to 



Intogrcitoil Circuits* 

P«No. Product Nn. L2 Lftl 

4W79 7400 ^ 11^ 

49015 , .-Hi ,1^ 

49040 7404^ A9 

49Q9I 7406 35 ^5 

49120 7407 IS ^5 

mU 7408 . 35 ^5 

4W»9 7410 « ^ .19 

47728 7417 ™35 ^5 

SOOOtt 7420 J!9 J5 

M135 7452 — 35 ^5 

SW20 7447 .79 

5055 1 7474 39 J.9 

50593 7476 .45 35 

50665 7486 45 -35 

50681 7489 .2,95 2.75 

50690 7490 59 .49 

49S12 74121 ,49 39 

49912 74192 . ,79 .69 

49939 74193 ^ ......... ,79 M 

UiiMr ICS* 

Emlifli Pfoduci No. hS 

3324 1 TLOSJCP 5.59 

2357^ m5'^ r ,. 39 

23683 ijuiTAM J5 

23771 LM336Z ™.l.09 

23851 LM339N ^ 

27422 NE555V .„.„„.,. J9 

2432a LM556N— ™ ,49 

24467 LM723CN ,49 

24539 LM74JCK ,29 

23131 LM1458N.. » 39 

23 1 57 LSi 1 4S8N „ ^ .45 

23181 LMH89N 45 

3427a ULN 2003 A . .69 

24230 LM3914N 2.49 

27385 NE5532 ^%A9 

51262 7805T, ,„ ^ *^,45 

5 1334 78 12T, ,,,, ,..„ ,. ,„. I ,.,„ *4S 



Pan 

NlL_ 



IC 



Sockets 



Priff 



51570 

57161 14LP 

37372 I6LP 

39335 24LP 

40301 2£LP 

41110 40LP 



S^piti 1™ pfofUe — ^ 10 
H'pin IdM proltk ^ A t 
16^n km ptulik ^ -12 
24-piti low prol^ ,19 
jA-ptn low profile .22 
40-p«n liiw profile ». .28 



ConiiMten 

Put Product 

^ No. 



Op,ctig6oo. Elks 



15114 DB25P Mile, 2Vpin, 

1 5 1 57 DB25S Fettuk 25 pin ^ .75 

15085 DB25H Hood^ 39 

15106 OB25MH MculHooti, *.«I35 

MiscellaiiMus 
Contponeiits' 

ftaitsistors And Diodes 



Put 


Prwlua 










DcKriptJoa 


Price 


28628 


PS2122 


TO-9> cue 


, , S.12 


28644 


PNI907 


TO-92 cuc_„ 


^32 


3599 J 


1K40» 


DO-41 


™30 


38236 


2N2222A 


TO- 18 cue ..^ 


-25 


36126 


1N4735 


DO-41 cnc a5 


3§359 


2N3904 


TO-92 C3ie_ 


12 


362M 


IN7SI 


DO 35 CMC 15 


38421 


2K4401 


TO 92 aa^^ 


— .35 


36038 


1N4I48 


DO-35euc„. 




38508 


2N3055 


TD-3C2M 






Switches 




Pmit 


Produa 












Price 


21936 


JMT123 


SPDT. 








on -on iio^t). 


-.31-15 


38842 


206^ 


SVS'l\ l6-p(n 








(DIP) 


.-«1.09 


26622 


MS 102 










™39 



Part No. 




FwKtwa 


41398 


41256-120 


2561: DIP 


42251 


5noo&P-M 


1MB DIP 


4!5Z3 


4i256A9B-S0 


256IC51MM 


41718 


42100aA9A-£0 


IMBSIPP 


41769 


42iO0QA9&^ 


1MB SIMM 



AAemo^^ 



.^$1.69 

1,99 

_ 1 6.95 
-«S4^ 
--54.95 



UDs 

Part No. Pmdmrt No. Docription Pfia 

34761 XC556G T1 3/4, (Gicen) 1.16 
34796 XC5S6R Tl 3M. (Rrdl — -12 
34825 XC^5GY Tl (YclTtjwl .16 



Call or write for your 
1993 Annual Catalog: 
1*800*637^8471 




24-Hour Toll' Free Order Hotline: 

1«800<831*4242 

J AMECO 

COMPUTE R PRO DUCTS 

1355 Shorcway Road 
Belmont, CA 94002 



^ $30.00 MintmiuQ OrdUr 
FAX: 1-8O0-237-6948 {D«™i 
FAX: 415-592-2503 nn^m-.«j) 
Jimcco SctviccLoc"* : 

Technical Supporti I *B00*83 1*0084 
BBSSuppon:4l5'637'9025 



For Intcrna[i(>n.il Sales, C 'us 10 me r Scmce. Credit Department and all other 
inquiries: Qli 4i^-V;2-Ha97 l>cim*cr^ 7AU^5VM P.S.T. 



CA Raidenis pinif acid jppliuhle uin 
[UpS^ iA»u.raiKc lie 



Termi: Pfko lubjcct to dwigc without notice, 
[tcmi lubjicct 10 jtrjikb^iy tad piiof talc 
Con]|i^jcic ]h|: of termi/wimaHei it nnrtiliyc 



9 !99^jMmfrv tOfSi All mScsaitu ut r^jtfcnd mdcbuiu of tbsr 



CIRCLE 114 OU FREE INFORMATION CARD 



FREE CATALOG! 
1-800-648-7938 

JERROLD HAMLIN OAK ETC 

CABLE TV 
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For an ottier informailon (702) 362^9026 



CABLETRONICS 

CONVERTERS 

1 -4Unl t» 5 Units 1 0 Unl ta 



PANASONIC TZP 1« 
STARGATE 2000 
^HAMLIN MCC 3000 



$88.00 
$79.00 
$25.00 



S75.00 S70.00 
569.00 $65.00 
$19.00 $15.00 



ADD-ON DECODERS 



&B-3 (NEW) $50.00 $45.00 

*SB-3 FACTORY $45.00 $39.00 

SA-3 S56.00 $50.00 

DTB-3 $65.00 $55.00 

KNI2A-2or3 $49.00 $45.00 

•"HAMI LIN MLO 1200-3 $49.00 $40.00 

*ZENITH SSAVr $1 65,00 $1 49.00 

SA^DF $159.00 $139.00 



OERROLD DPV7 
JERROLD DPBB 
SAesSO COMBO 
•JERROLD DRX-3-DIC 
JERROLD DR2-3-DIC 
*OAK M35B 
HAMLIN SPC 4000 3M 
ADD $1 0.00 FOR VAHISYNCH 



COMBOS 

$299.00 
$319,00 
$299,00 
$165.00 
$175.00 
$45.00 
$50.00 



$149.00 
5259.00 
S225.00 
$105.00 
$115,00 
$35.00 
$44.00 



$43.00 
$35.00 
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$50.00 
$40.00 
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$125.00 
$125.00 



S239.00 
S249.00 
$215.00 
$69.00 
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$30.00 
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*Befurbl8hed as New 



OTY 



IIEM 



CXJTPUT 
CHANNEL 



CAlJrornla Penal Qodt §B9^0 Forbldt ui from 
■hipping any cable d«sc rambling unit to 
anyons rffsldlna In the ttate of califomlB. 
Pikas iubject IP chaJtgs without notice. 



Please Print 



PRICE 
EACH 



SUB TOTAL 



Shipping Add 
S.00 Per unit 



300/0 wttlCard 
Add 5% 



TOTAL 



TOTAL 
PBiCE 



AddrKi_ 
Stale 



_C»t¥_ 



_-Sp_ 



O Caihier's Ch ^Iv □ M o/rey or def 
OViM OUC CCi 



_Tet:{ J_ 



□ goo 



DECLARATION OF AUTHORIZED USE- 1, Itie undersigned, do hereby declaie 
under penalty or perjury thai all products purcliaiad. now and In ffie tutuie, 
Mrill onljir be used on TV SYilemi udt^ aJi appitlcai>le fedv^ and stale laws. 
FEDERAL AND VARIOUS STATE LAWS PROVIDE FOR SUBSTANTIAL 
CRIMINAL AKD QVIL PENALTIES FOR UNAUTHORIZED USE. 



Data 



_Slfin&d_ 



Cabletronics 

9800 D Topanga Canyon Blvd., Suite 323, 
Chatsworlh. CA 91311 

For Free Calalog, or to place an order call 

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EASY work! E)(coEienl pay! AssembEe prtKluds at 
home. Call ton Irge 1 (flOO) 467*5566 Ext Sl92. 

HOME assembly work availabEc! Guaranmed 
easy fDorieyr Fme details* HOMEWORK*a Bfix 
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UONEYHAKERS! Easy! One marr CRT f^tCd- 
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MAKE S75, 000.00 to S25€,O0O-O0 yearly or mofO 
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DALL DISPLAY, Box 216Q-R. Van Nays. CA 
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CONTINGENCY paieni licensing. No fees ariy- 
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PACIFIC CABLE CO.. INC. 
732S'/ Reseda Blvd., Deot. 2UB 
Reseda. CA 91335 



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CHINESE HOROSCOPE 1-90lM4*06l1 12 00 Per Minut* 
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sive! "Free" details. COMMAND, Box 
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LEARN electronics and digital basics. Pm- 
grammei^ courses. Si 7 00 each, both S29.00. 
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SAVE $ importing radios, otoctrontcs... directly 
frpm manufaciuiefs. For business hobby. Guar- 
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Box e002'R. W^tchesier, OH 45069. 



I 



FUl-L- OR PARFTLMK J OB BUSINESS: 



I Learn VCR repair! 



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MUSICIANS, buikj a Ngh CfuaMy digilai delay, 
S10.00. very high Quality dyopfwnic synihesiief 
~ 510.00 KEts also availabte. GEBHAftOT Box 
754. Aj^aconda. MT S971I (406) 563-7506. 

BUILDING A Robo4: A Strawhtfoward Appccach. 
152 pages Jully illusiratod. Tn si ructions how you 
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I Sai A POWERUME ROAD, SUITE 103 
POWPANQ BEAOH. FL 3306S 



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COMPANY 



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TumtaNfl m sp&&d 
repair d VCfla. TVs 
Andmon. L«t» 
toctnevrt a«v4y 
turn unt for 
cemrntnt r«par. 20* 
Whto color l^el w^t: 

Super Horn Tweeter 



TJi& original 
pio;o Iwoetuf 
mrinufaclEirod 
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2.e3V/lM. 2&.30 

malelv lo walti} 
powflr tuindlino 

PftKJucttf cntp. 
cl0«n highs. 



Technician's Turntable Ptezo Super Tweeter 

f \ ^naB tweeter ^^^^^K 

[ ] ncofporiteS ■!! th« ^^^^H 

Frequfl'ncy rosponte: 



BBC 12" Dual Voice Coil 
Subwoofer 

Si^iQf qyajgty itaion 
i¥iBd* cast frame tSuai 
vtHca cod »i<?woo(«f . 



cai^ be f«oi^it«d 




4 KHi 27 KHx. 



FrtiqiMncy rasponsa; 

Odmeoijons MB" jc M'B' it 
3' ti6kt MotDTola iKSNlOOSA 

»RH-27£M>10 SS» $4" $3^* 

11079) (eO-i^iJ 

8" In- Wall Subwoofer 

0* ptfitit corM sutiwootor wits potyriof 
iMm ODNAfei^ OuMl w^ott' CDlb nwi B ohm 
irT«tdai)^p«rcoi^ PM4|AMeipefili«r 

" — 'UUHZL __ 

r hamflkx) capMbtfily 



SK-20KHI. SPL: 97„ 
tiantfiuig 80 vraita RMS. wt>e<i i^sd 
with a miCTofafBd capacitor- SoW jn 
pairs. Noi w^ighi 

#RH-265-267 $24«» $22* 

12 Ga. Speaker Wire 

Ex\m larg^ gflugo 

speakor wire for use ~ ^ 

wflh vOfV l^>9^ pOw*f ^1 
slereo systoms and tor >ii;_4^ 

in SKlj-dmAly long ^ 
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slrands of S6 ga wiio 
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eiij^^n multSplkit 
of Staet. 

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MdBlW/IM. Dimensions- 



nuionsa: 30-500 Hzl SO iMOlts RMS, 100 
watts m^i 



!0-5/8*tW) HW(U 1 3" 
hkrio dkmensiorts: 9 (W) 
N*1w<j*ght: Gibs 

#HH.300.430 l^^'^^' 

Parts 



IS' 



{L| 



S85«> $79^ 

(1-31 



340 E First St, Dayton, Ohio 454C»2 
Locah 1-513<222*0173 
FAX: 513<222-4644 





VCR Parts Assortment 




Fiaqtjancy response: 
45-tKMi SensiiJvrty; 
06.69 1W/1M VAS' 
3 73 cu fl . OTS^ 33a. 
BBC iSW32?/Fa Net 

#RH-294-130 



assonmcnl ot dips, 
wssh«f$, ^P'l^^^ 
sc/Bws. 10 pwc as 
eacti of 4 $iz«& d *E~ 

rings. 10 pieces of 14 
»iz»s of waiJiefi, 2 
eadt of 0 iteas qI 
tension and conifNttssion spnnos and 
?4 assorted scrowf. Tola! nl 34Q pieced. 



SI 39® 

(1-33 



$128*^ 



#nH-430'315 



S6» 

Ci'3) 



8 Ga. In-Li 



$5* 

ijp) 

Suction Cup Mount 
Fuse Holder Cellular Antenna 




Dw fooytwr BitoMe tiae ixAfaf wiii Q 



iwife For iiaa mMi AGU lyps hiM« Of 
reguUir AOC ham nvtion spring spauf it 
SO amp ma« at 12 wafts 

S2« 



The ideai anJenna iot 
ponab^e phones Suction 
cup grip mounli on inside 
of car. Mevor tuve yOMf oar 
vandalize ag^. Anlenna 
coRUK with 9 led of RG-S6 
w«fiTNC connector, 3 dB 
gain. Made in the U S A 




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4 30 morHy bac^ guaranty ' £20 00 niifurnufn order' We accept 
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on ordwt exe«e<^<ig 5 1». * Rvoign dastnaliDn od^omem please 
iendSSilDU.S finds for catatog pociage • 



S3^ 

it -9) (lO-yp) 

High Voltage Cap Kit 

85 pi«c« Hfl <»rdain$ a 
iqi»cfipn ol ZSO. 350. aiid 4S0 volt 
etetroiytic cwaaiors. 5 pmck 
oae*i oTl . 2.2, 3 3. 4.7. 6.8> 10. 22wf 
4nd 2 piecH each of 33. and 47uf , 
250V radial eapa. 5p<ec^«ac^of 
I. a.2. 3 3. 4.7, lOuf and 2 pieces 
each oi 22, 33uf. 350V factial capi 
5 pwc*S Oiicti of T, 2 2. 4.7uf and 2 
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KTSTERY 

Levitating Device 

Olfods float on ^ move to it« 
isudi. De§«s gravity* JWnaz^ 9ifL 
convefsdbon fMce, mage tiid( or 

AHniC €wiMii'¥lCH/Piana$l9.50 

FM Wireless 
Microphone! 

Crystal cieaf, u!im sensjti.s pickup 
transfl^its voices, sounds to any FM 
radio For security, monflonng 
chtsdfon, invaMs, Be M local 0J\ 

MVP1 Plan* S7.00 

MVPlKKil/Plint..,. $39 JO 





3IIIU 

Telephone 
Transmitter! 

AutomaticaHy transmits 2 sides ol 
phona conversation lo any FM rado, 
Tufiabfe, easy assembly PC boM 
Oparates <^ mften phone es n use. 

VWPlt7Plini $iM 

VWPUKTKaPlm ...... mM 





TV & FM Joker/Jammer 

cbsn«iTVof iad«[«oepliwL Gfoai 
9ag! Dtscralm requkod. Easy-buU 
eiearonic Kit. EJKIKi l . ... S19 JO 

100,000 V- 20' eange 
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Etadronic modulo, rnay be enclosed 
for handheW, poftato, of fixed im$. 
ITM2 Plant (craditabia lo kit} Sf 0.00 

rrwiK KHSPim 

BEAUY^TO-USE. AUTOMATIC 

Phone Recording 

Compr«t€ with ejil^nded ptay tape 
feoxder & Iin6 tntsflac^ $wticti. 
Automai^catty rec^ both sides of 

Pwp^t^i Raady to-Use Sysiim. 
TAPaUC Sytlm smJO 




INFORMATION UNUMITED^^ 

D6PIBE-4 60x716. Amherst NH 03 G31 \j>f^^^:Orbf 
mm 603-6734730 FAX 603-672-5406 
IICVISA,C00, Check Accepted. AO0S5S&K 



24 Kr Ofdtf Phone: 

80O-22M705 



Laser Pen 

Pan sii«d iasar, gn»i lor movies^ 
drive- ins. poirtfsr Rsajy lo use, <nCh 

Pocks! Laser Kit 

3nw or SflMr Uti Hiti sold M 
670nni tiode. Caurion. Pass irta item 
VRUKU 3{nw Luef Kit . . . $99 JO 
VH iaai gmwljgf Kit .. $119 J0 

mRElMm KM 

LASIKU 1mwUstr.e32mn.He»e 

EttytoBundKK ^9J0 

U SIKM 3mw VlfllOft,Kti $99 JO 

LAT05 Low Con HtNft Um luW, 
Jmw Tube & Ptans . . ooly S24 JO 

Otfiei pans avaiiabfo sepa^asely. 
GfBBl low Budgat Sctofjce Praj^ctl 

Stiocker Force Field 
^Vehicle Electrlfier 





M^ hand biib. shock wands 
eiectniy objeds^ cliafQo capaotors^ 
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CATALOG! 



with mmy more items! 
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All major brands carried 
♦JERROLD, *TOCOM, *ZEN1TII 
♦GENERAL INSTRUMENTS 
♦SCIENTIFIC ATLANTA, *OAK 
*HAMLIN, *EAGLE, ♦PIONEER 
7^ Year in business. Thank You 
Member of Omaha Chamber of Commerce 
1 Year warraniy on new equipment 
30 Day money back gtiaramee 
Orders shipped from stock wiihin 24 hours 

CALL TODAY FOR A FREE CATALOG 

1-800-624-1150 

CCD. 



%, 875 so. 72[»d Sl 

Omaha, NE 6StI4 



Cable TV 
Descrambler Kits 



Universal Ktt S55.00 

lndLid» aJ] psiti ind Boird Mot incJudtd 

Tri-Mode Kit S39.00 

Includes all oitrts, PC Board and AC AOoptor Not 

SB-3 Kit.., ,„S29-00 

rncluOar «JJ p«ris. PC Board and AC Aoaoior Not 
mcludftO s tn« enclosure 

Universal Tutorial .39.95 

anc) nvstrcubtesi-tooting NflU 

Tri-Mode TutoriaL, S9,95 

tnciijdes a ceie Cy pale Audy ot the prcdBt and has 
trQutii«naottfig hirvt. 

Snooper Stopper..., S39.00 

pTDiect yoiduc? troiTi Qttctvnbim daiaction ana 
t:50 tnt •ouutr. 



Call Toll Free 
1-800-258-1134 

M & G Electronics, Inc* 
301 Westminister Street 
Providence, Rl. 029Q3 



CIRCLE &a ON FREE tMFOAMATION CARD 



CIRCLE 197 ON FREf INFORMATION CAftO 



QUALITY PARTS - DISCOUNT PRICES - FAST SHIPPING 



Sman 
Neodymium 
Magnet 



n«od^um 

shape i!^mx. 0.S4" X 0.7" 
X O.r thick. Stiong lor Sis 
»ee. CATiMAG^ 
»1.SC each 



Digital Voice Module 



MIngf DVM-10B. Digital recording module 
vsped^!/ sufted for repfodudng verbal mss&ages, 
Ida<a3 for HAM ooni^stiing, memQ roc^ordor, verbal 
afarm $y&tom etc. Requires a mLfiimunt of external 
winng. Up lo 8 diltafent phrasa ctionnafcs. BuFtt-En SOOmW audb arnp'. 1 Mega- 
bit d DRAM memory, for up lo 32 second* o( reoorrfing. CofidariEflr or d/nomiq 
frtlw Input. Boafd size: 3 3/4' X 2" X r high. Includes memory chi|&s which re- 
quire InstaiTation. Microphone and oiher eiftemaJ oonponents not i^dudod. 
C AT# □ VM Eia S2 5 DO each 



A.C. Line Cordi 




6 * Black 18^ A.C, power csofds. SFH"-! intulation. Polartied plug. 
CAT«LCAC-7 2 for $1.00 *lOOfOfS45.00< 1000 for $400.00 



Car Lighter Coil Cord 



Piezo Element 



3Wtrtt 

Fieio EeJTBfit. 
Taiyo Yuden Co. n 
CB35B8KR4. 
&el-exdted ptezo 

1.40" diameier k 0.02 r thick. 

Re^Dfunt resialancs: 400 ohme. 

b* colorcoded leitds. 

CAT#PE-12 SLOOeach 
\ 0 for Sa.SO - 100 for $65IX) 



Flash Units 





NEW compact Itash asGentilies 
from a camora manufac!ur*r. 
Opaf*tes on 3 VtJc, t^ea^ureft 
2 1/r X 1 1/4', Edeal fof use us 
a strobe. warr\ing JIghl or atTen- 
tion getter. Inchjd«s a hook-up 
diagram. CAT*FSH-1 

eM:h • 10 lor $35,00 
100 rof S325,00 



12 Von 2 Amp 
Transformer 



Same as Mouser 
i4tF6020, 
12 VOL a Amp 
power transformer, 
r X 2.35' X 2.icr. 2,90- rnwnt- 
Ing centers. Pigtail leads. 
CAT* TX-iaaA S5 00 e^ 




LE.D/S 



Surface mount 
LED chip. 

Cleaf when ol. green when \H. 
Very itfty - whole untl Js 0. 115" 
X 0,055- X 0.05" thick, irrm 
(0.04'] lenn diametier. Gold- 
plated mounting suitaoes for 
superior conductivity. 
CAT#SMLED-2 10lor$£.00 
100 lor $18.00 
1000 lor St 40. 00 

StsndBrd JUMBO 

Diffused T sEze (S mm} 



RED CAT#LE[>-1 
lOlof St.SO- lOOtof $13,00 

GREEN CATN LED-2 
10 ter $2.00 • 100 for $1 7.00 

YELLQW CATN LEO^ 
10 for $2.00 * 100lor*17,00 

REDUCED PRiCBS 
FLASHING LED 

W/ buit In flashing cirojlt 
5 vol; operalkvi. T 1-3/4 

(5nnm) 



RED &0« each 
CAT#LED-4 to for $4.75 

GREEN 75c eadi 
CAT# LED-4G 10 lor $7,00 

YELLOW 75« each 
CAT* LEEMY 10 for $7.00 

LED HOLDER 

Two piece hokJer. 
CAT# HLEO 
10for65e 



ELECTROL UMINESCENT 
BACKLIGHTS 



Autormtivo Cigar lighter p^ug with ref)la09db1e 5 btt^ Tu««, CKiality, 
retractable coil cord extends to approxImaleV 3 leet. terminates with a 
5 pin OlH phjg which can bo cul- oft. Ideaf for banary chajger Of ornning 
1 1 2 Volt devices from car battery. CAT* CLP-IS $ 1 .50 each - 10 for $1 2.50 



D.a Walt Transformers (120 Vac INPUT) 



At lasll AkwCD^l etectrotuminesoenl 
gbwsirip and Inverter. These brand- 
new unhs were desigriod to bac^klight 
srr.ajl LCD TVs made by the Git lien 
Watdh conpany. The inverter drcuft 
changes 3 or 6 Vdc to oppro^^ Im^iTely 
1 DO V^H the voltage required to tight the 
gtowsirip. Lumlnooosni aurfaca area Is 
1,7* X 2,25*. ThOElrlp is a saJmon coEor 
In He oH state, and glows vrtiito wtien 
energized. The circuit board is 2.2^ X r. 
Glow strip and drcuhry car) be removed 
easiSy from pla&ilc hou&ing. Ideal lor 
spedal lighting etfedSr 

Citizen* 92TA operatea on 3 6 Vdc 
CATfBLU.t2 $3.50 each 
LARGE aUAfnJTY AVAILABLE 

10 for $32.00 • 100 for $275.00 



Monoral Equalizer 







Plufl St 


Yt« 






Pt1« 


4 Vdc 


70 ma. 


2.5 mm co-iw 


negative 


[>CTX-47tJ 


IZOO 


flVdte 


300 mo. 


2.1 mr 


n CO- ax 


positive 


DCTX-KJa 


$Z75 


e.3Vdc 


to ma. 


battery 




DCTX^IO 


$1.50 


9 Vdc 


300 rt^ 


2.1 mr 


n cO'a:K 


poehlve 


DCTX »32 


$aoo 


12 Vdc 


t oo ma. 


2 J mr 


pcoax 


negative 


DCTX^1210 


$2^50 


t2Vdc 


500 ma 


2.1 mr 


n CO- ax 


negative 


DCTX-125 


$4.50 


12 Vdc 


800 mi. 


2,5 mr 


noo-ajt 


positive 


DCTX-1281 




12 Vdc 


1 Arrp 


none 






DCTX-121 


S6.S0 


14 Vdc 


700 ma. 


1.3 mr 


n Co- ax 


negative 


PCTX-147CI 


$5.25 


IS Vdc 


400 ma. 


2.5 mr 


nCQM 


negative 


DCTX-1540 


$4.50 



SB 




v£fiYSPEaALOEAL 1 w WATT SWITCHING 
";^Sc^S" , POWER SUPPLY 



New 17 Vdc. 
210 ma wall 

iransformofs. 
6 ft. cord. 
Unusual 
co-ax la! device On end of 
oord can be cut oil and used 
lor another application. 

Large quant t;/ avarJabte. 
CAT* DCTX*1721 $1.50 each 
100 for $1.25 eiM:h 
1000 lof 11,00 ftach 





Rechargeable Batteries (nickehcadmlum) 




Five baAd graphic eQuaizer. AJbwG use 
of one source for bad^groond muafe and 
muslc-on-hold, Albws you to equalize 
and adjust the volume of one without 
changing the other. Us etui in any appfi- 
calbn where oqualLiallon of a monorai 
source Is des rrab^a. RCA |adk inputs and 
outputs. Ren^ovatJle met^ oontrol cover 
lo prevent tampering. 6,75' X 5.75" X 
3.125- high. CATi EQ-1 $15,00 each 



10 AMP SOLID 
STATE RELAY 



(USED) 
tOwrp 
solid stale 
relays, removed 
from equipment and tested. 
iDontfol vo^tagu: 250 volts AC 
at lOarrpS. Standard 'hock- 
ey- piick" size: 2.27- X 1 .TT X 
0,95-. UL aiHl CSA l^ted 
CAT*SSRLY>11U 
$a.25each - 10 for $30.00 



LCD Display • 40 Character X 2 Line 



BCWATT 
Computer Products « Xl4O^8301 
Input: 115™) Vac 
Output: -12 Vdc<g*0,2A 
12Vdo@»2.0A 
5.1 Vdc #3.5 A 
SwItcKlng power supply. 
ReguEated, 6 30* X 3.93" X 1.9' high. 
CAT#PS^5I $15.00 each 

75 WATT 

Cwi^of Prodt>cU i XL50^S6dl 
Inputt 11 5/230 Vac 
Output: -12 Vac #1,0 A 
12 Vdc 1,0 A 
5 Vdc @ 6.0 A 
Regulated twHcbing power sui^pV. 
7.75* X 4,25' X 1,78' high 

CAT* PS-Ttt $20,00 e*ch 



12 VDC STEPPER miOR 



AAA 


1.20 leOmAh 


ik:&j^aa 


$1.50 


$13*50 


AA 


1.20 600 mAh 


>*C&^A 


$200 


$1S,50 


AA«r/ 










SotdBfTcba 


1.20 600 mAh 


NCB^AA 


$2.20 


$20.00 














1,20 1200 mAh 




$4J^5 


$40.00 


C 


1.20 1200 mAh 


NCB^ 


$4.25 


140.00 


C Heavy Duty 


1.25 leOOmAh 


MDm:B^ 


$5.25 


$42.50 


0 


t.20 1200 mAh 


NCB-D 


$4.50 


$42-50 


D Heavy Duty 


1.25 4000 mAh 


HOHCB^D 


$7,00 


$65.00 




Op«rex f DMC40218 or HItacH # LMOISl 
Buitt inconiro^rar>ddrTvers.4 Of fibll operation. 5 Vdc power. 
Dl^lay size: 8,05' X 0.7" ii^oduie size: 7. 12^ X 1 .34'. Character ske: 
|SX7do£Ej 3.2mm X 4.85 rrni. Data sheeis and irtemjct'onsavflaable. 
CATJLCD-^ $l5.00eadl 




Alrpaxi A83712 M1 
1 2 Vdc. 36 ohm oof 1 15 degreei'step. 
2.25'dia,X0.9SMhic< 
0.25^ shah X O.e- tong. 
CAT«StfT-i $6,00 each 



ORDER TOLL FREE 1-800-826-5432 



Call Or Write 

For A 
Free 64 Page 

Catalog 

Outside the U.S,A. 
sand $2.00 postage. 



FAX (818) 781-2653 ■ INFORMATION (818) 904-0524 

Minimum Ordar $10,00* A\l Orders Can Be Charged To Visa, Mastercard Or Discovercard • 
Checks and Mormy Orders Accepted By Mail • Cafifomia, Add Sales Tax * No CCD. - 
Shippmg Arid Handling $3.50 for the 43 Continental United States - AH Others tnduding Alaska, Hawaii, 
P.R. And Canada Must Pay Futi Shipping ■ Quantities Limited * Pri^^s Subject to change without notice. 




MAIL ORDERS TO: ALL ELECTRONICS CORP • P.O. BOX 567 • VAN NUYS, CA 91408 



105 



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"CABLE BOXES" 
BELOW WHOLESALE 

GUARANTEED STOCK - COO'S 



106 



DESCRAMBLERS 



(QTY) 


(10) 


(20) 


(40) 


NEW TBI-3 


70 


55 


CALL 


TB 2 or 3 


45 


40 


CALL 


SA 38 


45 


40 


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OAK N^12 


43 


38 


CALL 


SB 2 OR 3 


43 


38 


CALL 


COMBINATION UNITS 


DRX^OIC 


89 


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SYL DIG 


59 


CALL 





PIONEER 295 275 CALL 
- CONVERTERS Wm EMOTES - 

PANASONIC- 
TZPC145 65 60 CALL 

STARQUEST^ 
E-Z550 65 60 CALL 
E-ZY550 75 65 CALL 

TM£FT OF 3EHVtC£ IS A. CRIME IKSTALL^N3 ANY OEVCE 
WITHOUT PERM|-S&tO>* W^T f^UEJJfCt tOU TO ClVJL Ofl 
CniMINAt, PENALTIES VOU MUST CHECK WITH tOUR 
LOCAL CABLE COMPANY ANO f*AY FOFI ALL SERVICE VOU 
use IT IS NOT ThEfNTENTOFlAKE SYLVAH TO E^EFnAUDi 
ANY TELEVISION OPEflATQF! AhO WE WILL NOT ASSIST ANY 
COMf*ANY OH INDJVIOUAL tN 00\t4G THE SAME 

LAKE SYLVAM SALES, INC. 

SORRV NO M(NNESOTA SALES 



CALL FOR A CATALOG NOW!! 

800-800-4582 



QRCLE 176 ON FREE INFORMATION CARD 



THE ELECTHONIC GOLDMINE 




electrwic us Miii^ in 
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IHEXPENSn^ CEtO£ft 

couKTER mr 

[>ii«di! bati Bd.i tf.i C^rrri, Hjij* 

C6447 S39« 



PRECmCN 
mCH SPEED 



G2>H> r^' Eil lll:S.'* 




;atai.og 



G2741 




MUSIC 
MODtJLC 

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paijf ThoEO fiv t:^^ piw R 

ci^iii»a4 ^pe mr.t< tfrt m^Mtl mq 
yrij ^ 1.<n CiH iflt.- S j i ir wa-? Fa» 

OjU'. HV haflnV tiMitt J|t cn a E-n^ 
Tt: t>.\yir El^l*ry rut nOvi^oO bt< 0[><r 
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f^Mj |W* ttffi fax* ify caa ami t 
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CONTROt PANEL 

luvi iiic Urn •^•..KkA cml 



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VTb flffiiupt MC, Visa and Money Ortters 
SEND ORDEflS TO; ^le tifxtrorw OoJdrrsw 

PHOriE [502) 4Sl'7*S4 FA3C ORDERS [SO?) 4Sl-949(S 



ADVERTISING INDEX 



Electronics Now does not assume any responsibility for errors that may appear in the 
index beJow. 



Free loformatron Number Page 

iO« AMCSiilw , 

75 Acc in-oUiiet*! H7 

107 All Klccfronics = , I OS 

— Amazing Concepts . _ J(H 

1S7 Am<:rican Rirliatice Inc .HI 

193 ilci-kman IndLi.strJal 16. 17 

194 BeckmaEi Indu.stnal . _ 26, 27 

98 Bi-ckman Industrial C V4 

109 C^SSates B 

— CIE.._ IK 25 

iSS CabJe Wart-house. 9i) 

— Cablet ronics , 1 1}2 

— Chenesko EVoduets , . , , > .v. , , 87 
^ Comniatid Productions, ....... 8.1 

127 Dcco Indu^strivs 87 

188 Electronic Gold mine . . _ . . l . . 106 

— Kk'ClroniCs<> Book Cluh 7 

— Electronics Engineers lt*C» , , . , 2H 
121 Flukt Manufacturing , CV2 

— 47tli Street Photo 34 

182 Global Specialties .3 

189 Goldstar I*reclsioii IS 

— Grantham College. ........... 59 

86 Heattikit 9(1 

— Hij^hText Publications, Inc - 1 7 

— tSCET,... 16 

U4 Janieco 100. 101 

183 Kijliin, _.5 

178 Kepco Po>*er Supply 86 

1 76 Lak e Sy I ui n Sales, Inc 106 

197 M&G Electronics , . , 104 

8? MCM Electronics 99 

53 MD Electronics 104 

93 Mark V, Eleclronioi 98 

1 17 Mouser . _ , 86 

— NRI Schools. . . , 18 

71 NTE Kleclronics 23 



IHl 

IK6 

180 

56 

184 



179 
177 

192 
190 
195 
191 



Northeast KlfCtriUiics 83 

Nu 111 Iter One Systems Ltd 93 

Oploelcctnuiics CV3 

Parts Express 103 

Ftop|e*s Crollege 46 

R.E. Video Offer 95 

Star Circuits 87 

TECI ..96 

Tech Spray , , , 12 

ilie SPEC-t OM Journal 26 

ILS. Cable ,.. Ki 

Vtejo Ihibli cat ions 82 

Xandi Elcclromas H7 

Zentek Corp. 81 



ADVERTISING SALES OFFICE 
Gertisback Publicfiticinsi Inc. 
500 B Bt'County Biwd, 
Fai-miitgdale, NV 11735 
1(5163 293 3000 
PTesident: Lnrry Sleekier 
For Advertising ONLY 
51B 293 3000 
Fax 1516-293 3115 
Larry Sleekier 

publisher 
Christina Estrada 

assistant to the President 
AHine Fishman 

t)dv£rrtjsing director 
DenSse MuN^n 

advertising assistant 
Kelly McQuade 

credit manager 

Subscriber Customer Seniioe 

1-800 '288 0652 

Order Entry for New SubscHbera 

1-S00999'7i39 

7:00 AM ' S:00 PM M-F MST 

ADVERTISING SALES OFFICES 

EAST/SOUTHEAST 

Stanley Levitan* Eastern Advertising Sales 

Man tiger 

Etectronics Now 

1 Overlook Ave. 

Great Neck. NY 1t021 

t 516-487-9357. 1*516-293-3000 

Fan 1-516 487-6402 

M10WEST/Texas/Ark«insas/0kEa. 

Ralph Bergen. Midwest Advertisir>g Sales 

Manager 

Electronics Now 

One Northfieid Pfaia, Suite 300 

NorlhfieEd, 11 60093-1214 

1-708-446-1444 

Fax 1 -708-559-0562 

PACIFIC COAST/Mountain States 
Artine Fishin<)n 

500 B 8i-County Blvd. 
Farmingdale. NY 11735 
1-£St63 293-3000 
FaxV516'a93-3ll5 
EN Shopper 

Joe Shere, National Representative 
RO. Box 169 
Idyllwild. CA 92549 
1-714-659-9743 
Fax t'7 14-659-2469 



CJRCLE laa ON FREE INFORMATION CAflO 



You want a 
bargraph & a full 
range counter - 
Pptoelectronics 
can deliverf 




BLEMO 

111 lJiT-3Ttf- *1 ^ 



Now for a limited time only. Si 60. 
off the list price, for our Full Range 
Model 2810 witfi bargraph - plus: 



Full range -10Hz to 3GHz. 

► LCD display (daylight visibility), 

• True state-of-the-art technology 
with the high speed ASIC. 

• NiCads & Charger included. 

• Ultra-high sensitivity 
•4 fast gate times. 

• Extruded metal case. 

• Compatible with MFJ207. 



Suggested options 
TAIOOS; 

Tefescoping Whip Antenna.,*. .$ t2. 

CC30 

Vinyt Carry Case,... S 15. 

BL28: 

EL Backlight for use in roomlight and low 
light .S 45. 

TCXO 30s 

Precision i.0.2ppm 20 to 40"C temp, 
compensalod lime base ....$100, 



Universal 
Handi-Counler" 
Model 3000, S375. and 
Bench Model 8030. S579. 
Both offer frequency, 
period, ralto and time 
intervaL 



Call for free catalog - Factory Direct Order Line: 
FL (305)771 -2050 • FAX (305)771-2052 



5S21 NE 14th Ave, • FL Lauderdale, FL 33334 
5^0 Ship/Handling (Max. SlO) U.S. & Canada. 
15% outside corttinenial U.S. A, 
Visa and Master Card accepted. 

CIRCLE W ON rREE INFORIMTION CAtiO 



TheDMMour 
customers desisned. 






fiufBcffmHofsfgr 



Before we built the new generation IJcckman 
InclLisirial Series 2000 DMMs, we asked people 
like you what you rmliywml. 

You want more. Mc)re test and iTieasureiDeni 
capabilities. Moa* imiible-shooting features. All 
in an affordable hand-held Vmi The Series 20CK) 
features the widest ninge PrequenCT Counter in 
any professional DMM. a full-range Cajxicitance 
Meter, True RMS measurements, Iniermineni 
Detection, 50ns Pulse Detection, and Pc*;ik 
Measurement capabilities. Plus, the Series 2000 
Ls tlie only meter to offer autoianging Min/Nlax 
reairding and relative modes. 

You want a DMM that*s easier to use, Tlie 
Series 2000*s display is 25% larger, %^'ith bigger 
digiLs and backlighting for easier reading, even 
in the worst light. Plus the fast 4 digit display 
provides the Itigli absolution needed for adjusting 
power supplies anti generators down to ImV. 
And only the Scries IWfy features a menuing 
system for fast, simple feature access. 



il. 

r,.l. J, 



MadU in Eht' USA 



An AfMate Of Emerson Eiectric Co. 



The lieckman Industrial Series 2000, priced 
from $209 to $279 olTer.s yovi the best perfor- 
mance for your dollar. Look again at tliese featunes; 

• i Digit, 10,000 Count Rescilution 

• Basic Accuraiy to (11% 

• True RMS. AC'or AC on DC 

• O.om Rc*solution 

• Automatic Reading Hold 

• 1ms Peak Hold 

• FuUy Auiorangtng Rebtive and Min Max Modes 

• Intennitient Detector 

• 111244. IHCIOIO Design 

• 'UxTLV Year Warranty 

The Series 2O0O offers tlie mn solutions ftjr your 
e\cn'ci;u test and measurement needs. Tlie only 
I )MMs designed by the pe(>ple who asc litem. You. 

Ft>r jnore infomiatitm m ihvsc new DMMs 
call {outside CA) 1-80O-H54-27O8 or 
(inside CA) 1-800-227-9781. Becknian 
Industrial 0)rporation. 3883 Rtiffin Rd.. 
San !>iego, CA mi^im. 



Spccdk^ w isihiea h> wthoui mtk^ 




CinCL£ 98 bM FREE INFORMATION CARD